Chord Energy (WLLBW) 10-Q 1 Aug 19 2019 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2019	Jul. 24, 2019
Document and Entity Information [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Jun. 30, 2019
Entity File Number	001-31899
Entity Registrant Name	WHITING PETROLEUM CORP
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	20-0098515
Entity Address, Address Line One	1700 Broadway, Suite 2300
Entity Address, City or Town	Denver
Entity Address, State or Province	CO
Entity Address, Postal Zip Code	80290-2300
City Area Code	303
Local Phone Number	837-1661
Title of 12(b) Security	Common Stock
Trading Symbol	WLL
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		91,298,629
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Entity Central Index Key	0001255474
Amendment Flag	false

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 6,680	$ 13,607
Accounts receivable trade, net	292,972	294,468
Derivative assets	25,971	68,342
Prepaid expenses and other	17,427	22,009
Total current assets	343,050	398,426
Property and equipment:
Oil and gas properties, successful efforts method	12,618,237	12,195,659
Other property and equipment	168,771	134,212
Total property and equipment	12,787,008	12,329,871
Less accumulated depreciation, depletion and amortization	(5,391,064)	(5,003,509)
Total property and equipment, net	7,395,944	7,326,362
Other long-term assets	36,732	34,785
TOTAL ASSETS	7,775,726	7,759,573
Current liabilities:
Current portion of long-term debt	542,716
Accounts payable trade	85,261	42,520
Revenues and royalties payable	186,647	228,284
Accrued capital expenditures	89,049	73,178
Accrued liabilities and other	65,796	69,013
Accrued interest	56,832	55,080
Accrued lease operating expenses	40,527	37,499
Taxes payable	28,088	31,357
Total current liabilities	1,094,916	536,931
Long-term debt	2,303,864	2,792,321
Asset retirement obligations	133,410	131,544
Operating lease obligations	13,000
Deferred income taxes		1,373
Other long-term liabilities	29,909	27,088
Total liabilities	3,575,099	3,489,257
Commitments and contingencies
Equity:
Common stock, $0.001 par value, 225,000,000 shares authorized; 91,891,065 issued and 91,298,629 outstanding as of June 30, 2019 and 92,067,216 issued and 91,018,692 outstanding as of December 31, 2018	92	92
Additional paid-in capital	6,419,093	6,414,170
Accumulated deficit	(2,218,558)	(2,143,946)
Total equity	4,200,627	4,270,316
TOTAL LIABILITIES AND EQUITY	$ 7,775,726	$ 7,759,573

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Jun. 30, 2019	Dec. 31, 2018
CONDENSED CONSOLIDATED BALANCE SHEETS [Abstract]
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	225,000,000	225,000,000
Common stock, shares issued	91,891,065	92,067,216
Common stock, shares outstanding	91,298,629	91,018,692

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
OPERATING REVENUES
Oil, NGL and natural gas sales	$ 426,264	$ 526,403	$ 815,753	$ 1,041,486
Revenue from Contract with Customer, Product and Service [Extensible List]	us-gaap:OilAndGasMember	us-gaap:OilAndGasMember	us-gaap:OilAndGasMember	us-gaap:OilAndGasMember
OPERATING EXPENSES
Lease operating expenses	$ 86,987	$ 75,323	$ 171,064	$ 155,744
Transportation, gathering, compression and other	11,128	11,137	20,969	22,608
Production and ad valorem taxes	39,420	46,023	67,576	84,002
Depreciation, depletion and amortization	203,009	199,294	401,141	387,213
Exploration and impairment	13,406	13,787	33,155	29,073
General and administrative	32,573	31,601	67,547	63,081
Derivative (gain) loss, net	(24,877)	103,483	38,028	156,147
(Gain) loss on sale of properties	1,063	(1,090)	1,086	1,486
Amortization of deferred gain on sale	(2,326)	(2,925)	(4,697)	(5,829)
Total operating expenses	360,383	476,633	795,869	893,525
INCOME FROM OPERATIONS	65,881	49,770	19,884	147,961
OTHER INCOME (EXPENSE)
Interest expense	(48,728)	(48,331)	(96,827)	(101,230)
Loss on extinguishment of debt		(808)		(31,968)
Interest income and other	642	1,489	958	2,369
Total other expense	(48,086)	(47,650)	(95,869)	(130,829)
INCOME (LOSS) BEFORE INCOME TAXES	17,795	2,120	(75,985)	17,132
INCOME TAX EXPENSE (BENEFIT)
Deferred income tax expense (benefit)	23,482		(1,373)
NET INCOME (LOSS)	$ (5,687)	$ 2,120	$ (74,612)	$ 17,132
INCOME (LOSS) PER COMMON SHARE
Basic (in dollars per share)	$ (0.06)	$ 0.02	$ (0.82)	$ 0.19
Diluted (in dollars per share)	$ (0.06)	$ 0.02	$ (0.82)	$ 0.19
WEIGHTED AVERAGE SHARES OUTSTANDING
Basic (in shares)	91,286	90,940	91,261	90,916
Diluted (in shares)	91,286	91,869	91,261	91,821

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019	Jun. 30, 2018
CASH FLOWS FROM OPERATING ACTIVITIES
Net income (loss)	$ (5,687)	$ (74,612)	$ 17,132
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation, depletion and amortization	203,009	401,141	387,213
Deferred income tax benefit	23,482	(1,373)
Amortization of debt issuance costs, debt discount and debt premium		15,734	15,342
Stock-based compensation		8,617	6,096
Amortization of deferred gain on sale	(2,326)	(4,697)	(5,829)
Loss on sale of properties	1,063	1,086	1,486
Oil and gas property impairments		13,179	18,310
Loss on extinguishment of debt			31,968
Non-cash derivative loss		42,371	77,931
Payment for settlement of commodity derivative contract			(61,036)
Other, net		3,492	188
Changes in current assets and liabilities:
Accounts receivable trade, net		(1,813)	(4,620)
Prepaid expenses and other		3,453	984
Accounts payable trade and accrued liabilities		20,261	44,977
Revenues and royalties payable		(41,637)	8,701
Taxes payable		(3,269)	4,437
Net cash provided by operating activities		381,933	543,280
CASH FLOWS FROM INVESTING ACTIVITIES
Drilling and development capital expenditures		(425,349)	(379,456)
Acquisition of oil and gas properties		(4,507)	(8,529)
Acquisition deposit held in escrow			(13,000)
Other property and equipment		(8,233)	(2,238)
Proceeds from sale of properties		15,444	923
Net cash used in investing activities		(422,645)	(402,300)
CASH FLOWS FROM FINANCING ACTIVITIES
Borrowings under credit agreement		1,160,000	962,265
Repayments of borrowings under credit agreement		(1,120,000)	(962,265)
Redemption of 5.0% Senior Notes due 2019			(990,023)
Debt issuance costs			(10,619)
Restricted stock used for tax withholdings		(3,693)	(3,104)
Principal payments on finance lease obligations	(1,258)	(2,522)
Net cash provided by (used in) financing activities		33,785	(1,003,746)
NET CHANGE IN CASH AND CASH EQUIVALENTS		(6,927)	(862,766)
CASH AND CASH EQUIVALENTS
Beginning of period		13,607	879,379
End of period	$ 6,680	6,680	16,613
NONCASH INVESTING ACTIVITIES
Accrued capital expenditures and accounts payable related to property additions		$ 122,098	$ 87,097

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical)	Jun. 30, 2019	Sep. 30, 2013
5.0% Senior Notes due 2019 [Member]
Interest Rate (as a percent)	5.00%	5.00%

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF EQUITY - USD ($) shares in Thousands, $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Total
BALANCES at Dec. 31, 2017	$ 92	$ 6,405,490	$ (2,486,440)	$ 3,919,142
BALANCES (in shares) at Dec. 31, 2017	92,095
Increase (Decrease) in Shareholders' Equity
Net income/loss			15,012	15,012
Restricted stock issued (in shares)	432
Restricted stock forfeited (in shares)	(96)
Restricted stock used for tax withholdings		(3,104)		(3,104)
Restricted stock used for tax withholdings (in shares)	(105)
Stock-based compensation		4,563		4,563
BALANCES at Mar. 31, 2018	$ 92	6,406,949	(2,471,428)	3,935,613
BALANCES (in shares) at Mar. 31, 2018	92,326
BALANCES at Dec. 31, 2017	$ 92	6,405,490	(2,486,440)	3,919,142
BALANCES (in shares) at Dec. 31, 2017	92,095
Increase (Decrease) in Shareholders' Equity
Net income/loss				17,132
BALANCES at Jun. 30, 2018	$ 92	6,408,482	(2,469,308)	3,939,266
BALANCES (in shares) at Jun. 30, 2018	92,185
BALANCES at Mar. 31, 2018	$ 92	6,406,949	(2,471,428)	3,935,613
BALANCES (in shares) at Mar. 31, 2018	92,326
Increase (Decrease) in Shareholders' Equity
Net income/loss			2,120	2,120
Restricted stock issued (in shares)	19
Restricted stock forfeited (in shares)	(160)
Stock-based compensation		1,533		1,533
BALANCES at Jun. 30, 2018	$ 92	6,408,482	(2,469,308)	3,939,266
BALANCES (in shares) at Jun. 30, 2018	92,185
BALANCES at Dec. 31, 2018	$ 92	6,414,170	(2,143,946)	4,270,316
BALANCES (in shares) at Dec. 31, 2018	92,067
Increase (Decrease) in Shareholders' Equity
Net income/loss			(68,925)	(68,925)
Restricted stock forfeited (in shares)	(106)
Restricted stock used for tax withholdings		(3,693)		(3,693)
Restricted stock used for tax withholdings (in shares)	(130)
Stock-based compensation		4,651		4,651
BALANCES at Mar. 31, 2019	$ 92	6,415,128	(2,212,871)	4,202,349
BALANCES (in shares) at Mar. 31, 2019	91,831
BALANCES at Dec. 31, 2018	$ 92	6,414,170	(2,143,946)	4,270,316
BALANCES (in shares) at Dec. 31, 2018	92,067
Increase (Decrease) in Shareholders' Equity
Net income/loss				(74,612)
BALANCES at Jun. 30, 2019	$ 92	6,419,093	(2,218,558)	4,200,627
BALANCES (in shares) at Jun. 30, 2019	91,891
BALANCES at Mar. 31, 2019	$ 92	6,415,128	(2,212,871)	4,202,349
BALANCES (in shares) at Mar. 31, 2019	91,831
Increase (Decrease) in Shareholders' Equity
Net income/loss			(5,687)	(5,687)
Restricted stock issued (in shares)	63
Restricted stock forfeited (in shares)	(3)
Stock-based compensation		3,965		3,965
BALANCES at Jun. 30, 2019	$ 92	$ 6,419,093	$ (2,218,558)	$ 4,200,627
BALANCES (in shares) at Jun. 30, 2019	91,891

BASIS OF PRESENTATION

BASIS OF PRESENTATION	6 Months Ended
	Jun. 30, 2019
BASIS OF PRESENTATION [Abstract]
BASIS OF PRESENTATION	1. BASIS OF PRESENTATION Description of Operations Condensed Consolidated Financial Statements Reclassifications — Adopted and Recently Issued Accounting Pronouncements Leases Leases

OIL AND GAS PROPERTIES

OIL AND GAS PROPERTIES	6 Months Ended
	Jun. 30, 2019
OIL AND GAS PROPERTIES [Abstract]
OIL AND GAS PROPERTIES	2. OIL AND GAS PROPERTIES Net capitalized costs related to the Company’s oil and gas producing activities at June 30, 2019 and December 31, 2018 are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ 2019 2018 Costs of completed wells and facilities ​ $ 9,546,167 ​ $ 9,182,384 Proved leasehold costs ​ ​ 2,734,887 ​ ​ 2,729,593 Wells and facilities in progress ​ ​ 228,164 ​ ​ 160,995 Unproved leasehold costs ​ ​ 109,019 ​ ​ 122,687 Total oil and gas properties, successful efforts method ​ ​ 12,618,237 ​ ​ 12,195,659 Accumulated depletion ​ ​ (5,313,661) ​ ​ (4,937,579) Oil and gas properties, net ​ $ 7,304,576 ​ $ 7,258,080 ​

ACQUISITIONS AND DIVESTITURES

ACQUISITIONS AND DIVESTITURES	6 Months Ended
	Jun. 30, 2019
ACQUISITIONS AND DIVESTITURES [Abstract]
ACQUISITIONS AND DIVESTITURES	3. ACQUISITIONS AND DIVESTITURES 2019 Acquisitions and Divestitures There were no significant acquisitions or divestitures during the six months ended June 30, 2019. 2018 Acquisitions and Divestitures On July 31, 2018, the Company completed the acquisition of certain oil and gas properties located in Richland County, Montana and McKenzie County, North Dakota for an aggregate purchase price of $130 million (before closing adjustments). The properties consist of approximately 54,800 net acres in the Williston Basin, including interests in 117 producing oil and gas wells and undeveloped acreage. The revenue and earnings from these properties since the acquisition date are included in the Company’s consolidated financial statements and are not material for the year ended December 31, 2018. Pro forma revenue and earnings for the acquired properties are not material to the Company’s condensed consolidated financial statements and have not been presented accordingly. The acquisition was recorded using the acquisition method of accounting. The following table summarizes the allocation of the $123 million adjusted purchase price to the tangible assets acquired and liabilities assumed in this acquisition based on their relative fair values at the acquisition date, which did not result in the recognition of goodwill or a bargain purchase gain (in thousands): ​ ​ ​ ​ ​ Cash consideration ​ $ 122,861 ​ ​ ​ ​ Fair value of assets acquired: ​ ​ ​ Accounts receivable trade, net ​ $ 30 Prepaid expenses and other ​ ​ 43 Oil and gas properties, successful efforts method: ​ ​ ​ Proved oil and gas properties ​ ​ 106,860 Unproved oil and gas properties ​ ​ 21,769 Total fair value of assets acquired ​ ​ 128,702 ​ ​ ​ ​ Fair value of liabilities assumed: ​ ​ ​ Revenue and royalties payable ​ ​ 3,309 Asset retirement obligations ​ ​ 2,532 Total fair value of liabilities assumed ​ ​ 5,841 ​ ​ ​ ​ Total fair value of assets and liabilities acquired ​ $ 122,861 ​ There were no significant divestitures during the six months ended June 30, 2018.

LEASES

LEASES	6 Months Ended
	Jun. 30, 2019
LEASES [Abstract]
LEASES	4. LEASES The Company adopted ASC 842 effective January 1, 2019, which replaces previous lease accounting requirements under FASB ASC Topic 840 – Leases The Company has operating and finance leases for corporate and field offices, pipeline and midstream facilities, field and office equipment and automobiles. Right-of-use (“ROU”) assets and liabilities associated with these leases are recognized at the lease commencement date based on the present value of the lease payments over the lease term. ROU assets represent the Company’s right to use an underlying asset for the lease term, and lease liabilities represent the Company’s obligation to make lease payments. Supplemental balance sheet information for the Company’s leases as of June 30, 2019 consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Leases ​ Balance Sheet Classification ​ June 30, 2019 ​ ​ ​ ​ ​ ​ Operating Leases ​ ​ ​ ​ ​ Operating lease ROU assets ​ Other long-term assets ​ $ 18,634 Accumulated depreciation ​ Other long-term assets ​ ​ (5,373) Operating lease ROU assets, net ​ ​ ​ $ 13,261 ​ ​ ​ ​ ​ ​ Short-term operating lease obligations ​ Accrued liabilities and other ​ $ 6,335 Long-term operating lease obligations ​ Operating lease obligations ​ ​ 13,000 Total operating lease obligations ​ ​ ​ $ 19,335 ​ ​ ​ ​ ​ ​ Finance Leases ​ ​ ​ ​ ​ Finance lease ROU assets ​ Other property and equipment ​ $ 34,237 Accumulated depreciation ​ Accumulated depreciation, depletion and amortization ​ ​ (14,424) Finance lease ROU assets, net ​ ​ ​ $ 19,813 ​ ​ ​ ​ ​ ​ Short-term finance lease obligations ​ Accrued liabilities and other ​ $ 5,003 Long-term finance lease obligations ​ Other long-term liabilities ​ ​ 17,170 Total finance lease obligations ​ ​ ​ $ 22,173 ​ The Company’s leases have terms of less than one year to 11 years. Most of the Company’s leases do not state or imply a discount rate. Accordingly, the Company uses its incremental borrowing rate based on information available at lease commencement to determine the present value of the lease payments. Information regarding the Company’s lease terms and discount rates as of June 30, 2019 is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted Average Remaining Lease Term ​ ​ ​ ​ ​ Operating leases ​ ​ ​ ​ 7 years Finance leases ​ ​ ​ ​ 5 years ​ ​ ​ ​ ​ ​ Weighted Average Discount Rate ​ ​ ​ ​ ​ Operating leases ​ ​ ​ ​ 4.9% Finance leases ​ ​ ​ ​ 9.0% ​ ​ Operating lease cost is recognized on a straight-line basis over the lease term. Finance lease cost is recognized based on the effective interest method for the lease liability and straight-line amortization of the ROU asset, resulting in more cost being recognized in earlier lease periods. All payments for short-term leases, including leases with a term of one month or less, are recognized in income or capitalized to the cost of oil and gas properties on a straight-line basis over the lease term. Additionally, any variable payments, which are generally related to the corresponding utilization of the asset, are recognized in the period in which the obligation was incurred. Lease cost for the three and six months ended June 30, 2019 consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ June 30, 2019 ​ June 30, 2019 Operating lease cost ​ $ 2,883 ​ $ 5,753 ​ ​ ​ ​ ​ ​ ​ Finance lease cost: ​ ​ ​ ​ ​ ​ Amortization of ROU assets ​ $ 1,381 ​ $ 2,778 Interest on lease liabilities ​ ​ 504 ​ ​ 1,024 Total finance lease cost ​ $ 1,885 ​ $ 3,802 ​ ​ ​ ​ ​ ​ ​ Short-term lease payments ​ $ 220,741 ​ $ 345,063 Variable lease payments ​ $ 5,840 ​ $ 10,775 ​ Total lease cost represents the total financial obligations of the Company, a portion of which has been or will be reimbursed by the Company’s working interest partners. Lease cost is included in various line items on the consolidated statements of operations or capitalized to oil and gas properties and is recorded at the Company’s net working interest. Supplemental cash flow information related to leases for the three and six months ended June 30, 2019 consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ June 30, 2019 ​ June 30, 2019 Cash paid for amounts included in the measurement of lease liabilities: ​ ​ ​ ​ ​ ​ Operating cash flows from operating leases ​ $ 2,637 ​ $ 5,415 Operating cash flows from finance leases ​ $ 503 ​ $ 1,021 Financing cash flows from finance leases ​ $ 1,258 ​ $ 2,522 ​ ​ ​ ​ ​ ​ ​ ROU assets obtained in exchange for new operating lease obligations ​ $ 2 ​ $ 11 ROU assets obtained in exchange for new finance lease obligations ​ $ 599 ​ $ 1,336 ​ The Company’s lease obligations as of June 30, 2019 will mature as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ending December 31, ​ Operating Leases ​ Finance Leases 2019 ​ $ 4,518 ​ $ 3,499 2020 ​ ​ 4,001 ​ ​ 6,399 2021 ​ ​ 1,891 ​ ​ 5,091 2022 ​ ​ 1,857 ​ ​ 4,014 2023 ​ ​ 1,608 ​ ​ 3,348 Remaining ​ ​ 9,232 ​ ​ 5,766 Total lease payments ​ $ 23,107 ​ $ 28,117 Less imputed interest ​ ​ (3,772) ​ ​ (5,944) Total discounted lease payments ​ $ 19,335 ​ $ 22,173 ​ As of June 30, 2019, the Company had a contract for an additional corporate office that consists of approximately $35 million of undiscounted minimum lease payments. The operating lease has a ten-year lease term. A portion of the lease is expected to commence in July 2019, and the remaining portion is expected to commence in June 2020. As of December 31, 2018, minimum future contractual payments for long-term leases under the scope of ASC 840 are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Pipeline ​ Automobile and ​ ​ Real Estate ​ Transportation ​ Equipment Year ending December 31, ​ Leases ​ Agreement ​ Leases 2019 ​ $ 7,407 ​ $ 3,180 ​ $ 4,216 2020 ​ ​ 4,770 ​ ​ 3,180 ​ ​ 3,422 2021 ​ ​ 4,066 ​ ​ 3,180 ​ ​ 1,678 2022 ​ ​ 4,188 ​ ​ 3,180 ​ ​ 488 2023 ​ ​ 4,017 ​ ​ 3,180 ​ ​ 35 Remaining ​ ​ 25,140 ​ ​ 5,565 ​ ​ - Total lease payments ​ $ 49,588 ​ $ 21,465 ​ $ 9,839 ​

LONG-TERM DEBT

LONG-TERM DEBT	6 Months Ended
	Jun. 30, 2019
LONG-TERM DEBT [Abstract]
LONG-TERM DEBT	5. LONG-TERM DEBT Long-term debt, including the current portion, consisted of the following at June 30, 2019 and December 31, 2018 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ 2019 2018 Credit agreement ​ $ 40,000 ​ $ - 1.25% Convertible Senior Notes due 2020 ​ ​ 562,075 ​ ​ 562,075 5.75% Senior Notes due 2021 ​ ​ 873,609 ​ ​ 873,609 6.25% Senior Notes due 2023 ​ ​ 408,296 ​ ​ 408,296 6.625% Senior Notes due 2026 ​ ​ 1,000,000 ​ ​ 1,000,000 Total principal ​ ​ 2,883,980 ​ ​ 2,843,980 Unamortized debt discounts and premiums ​ ​ (17,550) ​ ​ (28,994) Unamortized debt issuance costs on notes ​ ​ (19,850) ​ ​ (22,665) Total debt ​ ​ 2,846,580 ​ ​ 2,792,321 Less current portion of long-term debt ​ ​ (542,716) ​ ​ - Total long-term debt ​ $ 2,303,864 ​ $ 2,792,321 ​ Credit Agreement Whiting Oil and Gas, the Company’s wholly owned subsidiary, has a credit agreement with a syndicate of banks that as of June 30, 2019 had a borrowing base of $2.25 billion and aggregate commitments of $1.75 billion. As of June 30, 2019, the Company had $1.7 billion of available borrowing capacity under the credit agreement, which was net of $40 million of borrowings outstanding and $2 million in letters of credit outstanding. The borrowing base under the credit agreement is determined at the discretion of the lenders, based on the collateral value of the Company’s proved reserves that have been mortgaged to such lenders, and is subject to regular redeterminations on May 1 and November 1 of each year, as well as special redeterminations described in the credit agreement, in each case which may reduce the amount of the borrowing base. Upon a redetermination of the borrowing base, either on a periodic or special redetermination date, if borrowings in excess of the revised borrowing capacity were outstanding, the Company could be forced to immediately repay a portion of its debt outstanding under the credit agreement. A portion of the revolving credit facility in an aggregate amount not to exceed $50 million may be used to issue letters of credit for the account of Whiting Oil and Gas or other designated subsidiaries of the Company. As of June 30, 2019, $48 million was available for additional letters of credit under the agreement. The credit agreement provides for interest only payments until maturity, when the credit agreement expires and all outstanding borrowings are due. The credit agreement matures on April 12, 2023, provided that if at any time and for so long as any senior notes (other than the 2020 Convertible Senior Notes) have a maturity date prior to 91 days after April 12, 2023, the maturity date shall be the date that is 91 days prior to the maturity of such senior notes. Interest under the credit agreement accrues at the Company’s option at either (i) a base rate for a base rate loan plus the margin in the table below, where the base rate is defined as the greatest of the prime rate, the federal funds rate plus 0.5% per annum, or an adjusted LIBOR rate plus 1.0% per annum, or (ii) an adjusted LIBOR rate for a Eurodollar loan plus the margin in the table below. Additionally, the Company incurs commitment fees as set forth in the table below on the unused portion of the aggregate commitments of the lenders under the credit agreement, which are included as a component of interest expense. At June 30, 2019, the weighted average interest rate on the outstanding principal balance under the credit agreement was 4.4%. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Applicable ​ Applicable ​ ​ ​ ​ Margin for Base ​ Margin for ​ Commitment Ratio of Outstanding Borrowings to Borrowing Base Rate Loans Eurodollar Loans Fee Less than 0.25 to 1.0 ​ 0.50% ​ 1.50% ​ 0.375% Greater than or equal to 0.25 to 1.0 but less than 0.50 to 1.0 ​ 0.75% ​ 1.75% ​ 0.375% Greater than or equal to 0.50 to 1.0 but less than 0.75 to 1.0 ​ 1.00% ​ 2.00% ​ 0.50% Greater than or equal to 0.75 to 1.0 but less than 0.90 to 1.0 ​ 1.25% ​ 2.25% ​ 0.50% Greater than or equal to 0.90 to 1.0 ​ 1.50% ​ 2.50% ​ 0.50% ​ The credit agreement contains restrictive covenants that may limit the Company’s ability to, among other things, incur additional indebtedness, sell assets, make loans to others, make investments, enter into mergers, enter into hedging contracts, incur liens and engage in certain other transactions without the prior consent of its lenders. Except for limited exceptions, the credit agreement also restricts the Company’s ability to make any dividend payments or distributions on its common stock. These restrictions apply to all of the Company’s restricted subsidiaries (as defined in the credit agreement). As of June 30, 2019, there were no retained earnings free from restrictions. The credit agreement requires the Company, as of the last day of any quarter, to maintain the following ratios (as defined in the credit agreement): (i) a consolidated current assets to consolidated current liabilities ratio (which includes an add back of the available borrowing capacity under the credit agreement) of not less than 1.0 to 1.0 and (ii) a total debt to last four quarters’ EBITDAX ratio of not greater than 4.0 to 1.0. The Company was in compliance with its covenants under the credit agreement as of June 30, 2019. The obligations of Whiting Oil and Gas under the credit agreement are collateralized by a first lien on substantially all of Whiting Oil and Gas’ and Whiting Resource Corporation’s properties. The Company has guaranteed the obligations of Whiting Oil and Gas under the credit agreement and has pledged the stock of its subsidiaries as security for its guarantee. Senior Notes and Convertible Senior Notes The following table summarizes the material terms of the Company’s senior notes and convertible senior notes outstanding at June 30, 2019: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2020 ​ ​ ​ ​ ​ Convertible ​ 2021 ​ 2023 ​ 2026 ​ ​ Senior Notes ​ Senior Notes ​ Senior Notes ​ Senior Notes Outstanding principal (in thousands) ​ $ 562,075 ​ $ 873,609 ​ $ 408,296 ​ $ 1,000,000 Interest rate ​ 1.25% ​ 5.75% ​ 6.25% ​ 6.625% Maturity date ​ Apr 1, 2020 ​ Mar 15, 2021 ​ Apr 1, 2023 ​ Jan 15, 2026 Interest payment dates ​ Apr 1, Oct 1 ​ Mar 15, Sep 15 ​ Apr 1, Oct 1 ​ Jan 15, Jul 15 Make-whole redemption date (1) ​ N/A (2) ​ Dec 15, 2020 ​ Jan 1, 2023 ​ Oct 15, 2025 (1) On or after these dates, the Company may redeem the applicable series of notes, in whole or in part, at a redemption price equal to 100% of the principal amount redeemed, together with accrued and unpaid interest up to the redemption date. At any time prior to these dates, the Company may redeem the notes at a redemption price that includes an applicable premium as defined in the indentures to such notes. (2) The indenture governing the 1.25% Convertible Senior Notes due 2020 does not allow for optional redemption by the Company prior to the maturity date. Senior Notes In March 2015, the Company issued at par $750 million of 6.25% Senior Notes due April 2023 (the “2023 Senior Notes”). In December 2017, the Company issued at par $1.0 billion of 6.625% Senior Notes due January 2026 (the “2026 Senior Notes” and together with the 2021 Senior Notes and the 2023 Senior Notes, the “Senior Notes”). The Company used the net proceeds from this offering to redeem in January 2018 all of the then outstanding 2019 Senior Notes. Refer to “Redemption of 2019 Senior Notes” below for more information on the redemption of the 2019 Senior Notes. Exchange of Senior Notes for Convertible Notes. Redemption of 2019 Senior Notes. 2020 Convertible Senior Notes For the remaining $562 million aggregate principal amount of 2020 Convertible Senior Notes outstanding as of June 30, 2019, the Company has the option to settle conversions of these notes with cash, shares of common stock or a combination of cash and common stock at its election. The Company’s intent is to settle the principal amount of the 2020 Convertible Senior Notes in cash upon conversion. Prior to January 1, 2020, the 2020 Convertible Senior Notes will be convertible at the holder’s option only under the following circumstances: (i) during any calendar quarter commencing after the calendar quarter ending on June 30, 2015 (and only during such calendar quarter), if the last reported sale price of the Company’s common stock for at least 20 trading days (whether or not consecutive) during the period of 30 consecutive trading days ending on the last trading day of the immediately preceding calendar quarter is greater than or equal to 130% of the conversion price on each applicable trading day; (ii) during the five business day period after any five consecutive trading day period (the “measurement period”) in which the trading price per $1,000 principal amount of the 2020 Convertible Senior Notes for each trading day of the measurement period is less than 98% of the product of the last reported sale price of the Company’s common stock and the conversion rate on each such trading day; or (iii) upon the occurrence of specified corporate events. On or after January 1, 2020, the 2020 Convertible Senior Notes will be convertible at any time until the second scheduled trading day immediately preceding the April 1, 2020 maturity date of the notes. The notes will be convertible at a current conversion rate of 6.4102 shares of Whiting’s common stock per $1,000 principal amount of the notes, which is equivalent to a current conversion price of approximately $156.00. The conversion rate will be subject to adjustment in some events. In addition, following certain corporate events that occur prior to the maturity date, the Company will increase, in certain circumstances, the conversion rate for a holder who elects to convert its 2020 Convertible Senior Notes in connection with such corporate event. As of June 30, 2019, none of the contingent conditions allowing holders of the 2020 Convertible Senior Notes to convert these notes had been met. Upon issuance, the Company separately accounted for the liability and equity components of the 2020 Convertible Senior Notes. The liability component was recorded at the estimated fair value of a similar debt instrument without the conversion feature. The difference between the principal amount of the 2020 Convertible Senior Notes and the estimated fair value of the liability component was recorded as a debt discount and is being amortized to interest expense over the term of the notes using the effective interest method, with an effective interest rate of 5.6% per annum. The fair value of the liability component of the 2020 Convertible Senior Notes as of the issuance date was estimated at $1.0 billion, resulting in a debt discount at inception of $238 million. The equity component, representing the value of the conversion option, was computed by deducting the fair value of the liability component from the initial proceeds of the 2020 Convertible Senior Notes issuance. This equity component was recorded, net of deferred taxes and issuance costs, in additional paid-in capital within shareholders’ equity, and will not be remeasured as long as it continues to meet the conditions for equity classification. Transaction costs related to the 2020 Convertible Senior Notes issuance were allocated to the liability and equity components based on their relative fair values. Issuance costs attributable to the liability component were recorded as a reduction to the carrying value of long-term debt on the consolidated balance sheet and are being amortized to interest expense over the term of the notes using the effective interest method. Issuance costs attributable to the equity component were recorded as a charge to additional paid-in capital within shareholders’ equity. The 2020 Convertible Senior Notes consisted of the following at June 30, 2019 and December 31, 2018 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ 2019 2018 Liability component ​ ​ ​ ​ ​ ​ Principal ​ $ 562,075 ​ $ 562,075 Less: unamortized note discount ​ ​ (17,950) ​ ​ (29,504) Less: unamortized debt issuance costs ​ ​ (1,409) ​ ​ (2,340) Net carrying value ​ $ 542,716 ​ $ 530,231 Equity component (1) ​ $ 136,522 ​ $ 136,522 (1) Recorded in additional paid-in capital, net of $5 million of issuance costs and $50 million of deferred taxes. The following table presents the interest expense recognized on the 2020 Convertible Senior Notes related to the stated interest rate and amortization of the debt discount for the three and six months ended June 30, 2019 and 2018 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ June 30, ​ June 30, ​ ​ 2019 ​ 2018 ​ 2019 ​ 2018 Interest expense on 2020 Convertible Senior Notes ​ $ 7,574 ​ $ 7,258 ​ $ 15,068 ​ $ 14,439 ​ Security and Guarantees The Senior Notes and the 2020 Convertible Senior Notes are unsecured obligations of Whiting Petroleum Corporation and these unsecured obligations are subordinated to all of the Company’s secured indebtedness, which consists of Whiting Oil and Gas’ credit agreement. The Company’s obligations under the Senior Notes and the 2020 Convertible Senior Notes are guaranteed by the Company’s 100%-owned subsidiaries, Whiting Oil and Gas, Whiting US Holding Company, Whiting Canadian Holding Company ULC and Whiting Resources Corporation (the “Guarantors”). These guarantees are full and unconditional and joint and several among the Guarantors. Any subsidiaries other than these Guarantors are minor subsidiaries as defined by Rule 3-10(h)(6) of Regulation S-X of the SEC. Whiting Petroleum Corporation has no assets or operations independent of this debt and its investments in its consolidated subsidiaries.

ASSET RETIREMENT OBLIGATIONS

ASSET RETIREMENT OBLIGATIONS	6 Months Ended
	Jun. 30, 2019
ASSET RETIREMENT OBLIGATIONS [Abstract]
ASSET RETIREMENT OBLIGATIONS	6. ASSET RETIREMENT OBLIGATIONS The Company’s asset retirement obligations represent the present value of estimated future costs associated with the plugging and abandonment of oil and gas wells, removal of equipment and facilities from leased acreage, and land restoration (including removal of certain onshore and offshore facilities in California) in accordance with applicable local, state and federal laws. The current portions at June 30, 2019 and December 31, 2018 were $3 million and $4 million, respectively, and have been included in accrued liabilities and other in the consolidated balance sheets. The following table provides a reconciliation of the Company’s asset retirement obligations for the six months ended June 30, 2019 (in thousands): ​ ​ ​ ​ ​ Asset retirement obligation at January 1, 2019 ​ $ 135,834 Additional liability incurred ​ ​ 1,982 Revisions to estimated cash flows ​ ​ (7,511) Accretion expense ​ ​ 5,819 Obligations on sold properties ​ ​ (310) Liabilities settled ​ ​ 167 Asset retirement obligation at June 30, 2019 ​ $ 135,981 ​

DERIVATIVE FINANCIAL INSTRUMENT

DERIVATIVE FINANCIAL INSTRUMENTS	6 Months Ended
	Jun. 30, 2019
DERIVATIVE FINANCIAL INSTRUMENTS [Abstract]
DERIVATIVE FINANCIAL INSTRUMENTS	7. DERIVATIVE FINANCIAL INSTRUMENTS The Company is exposed to certain risks relating to its ongoing business operations, and it uses derivative instruments to manage its commodity price risk. In addition, the Company periodically enters into contracts that contain embedded features which are required to be bifurcated and accounted for separately as derivatives. Commodity Derivative Contracts — Crude Oil Costless Collars and Swaps. The table below details the Company’s costless collar and swap derivatives entered into to hedge forecasted crude oil production revenues as of June 30, 2019. ​ ​ ​ ​ ​ ​ ​ ​ Derivative ​ ​ ​ Contracted Crude ​ Weighted Average NYMEX Price Instrument Period Oil Volumes (Bbl) for Crude Oil (per Bbl) Collars (1) ​ Jul - Dec 2019 ​ 5,400,000 ​ $52.56 - $75.17 ​ ​ Jan - Jun 2020 ​ 728,000 ​ $55.00 - $67.33 Swaps (1) ​ Jul - Dec 2019 ​ 3,300,000 ​ $61.43 ​ ​ Jan - Jun 2020 ​ 2,184,000 ​ $58.88 ​ ​ Total ​ 11,612,000 ​ ​ (1) Subsequent to June 30, 2019, the Company entered into additional swap contracts for 250,000 Bbl of crude oil volumes for the remainder of 2019. Crude Oil Sales and Delivery Contract. Derivative Instrument Reporting table summarizes the effects of derivative instruments on the consolidated statements of operations for the three and six months ended June 30, 2019 and 2018 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (Gain) Loss Recognized in Income Not Designated as ​ Statement of Operations ​ Three Months Ended June 30, ASC 815 Hedges ​ Classification ​ 2019 ​ 2018 Commodity contracts ​ Derivative (gain) loss, net ​ $ (24,877) ​ $ 103,483 Total ​ ​ ​ $ (24,877) ​ $ 103,483 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Loss Recognized in Income Not Designated as ​ Statement of Operations ​ Six Months Ended June 30, ASC 815 Hedges Classification 2019 2018 Commodity contracts ​ Derivative (gain) loss, net ​ $ 38,028 ​ $ 156,147 Total ​ ​ ​ $ 38,028 ​ $ 156,147 ​ Offsetting of Derivative Assets and Liabilities. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2019 (1) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net ​ ​ ​ ​ Gross ​ ​ ​ ​ Recognized ​ ​ ​ ​ Recognized ​ Gross ​ Fair Value Not Designated as ​ ​ ​ Assets/ ​ Amounts ​ Assets/ ASC 815 Hedges Balance Sheet Classification Liabilities Offset Liabilities Derivative assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Commodity contracts - current ​ Derivative assets ​ $ 28,484 ​ $ (2,513) ​ $ 25,971 Total derivative assets ​ ​ ​ $ 28,484 ​ $ (2,513) ​ $ 25,971 Derivative liabilities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Commodity contracts - current ​ Accrued liabilities and other ​ $ 2,513 ​ $ (2,513) ​ $ - Total derivative liabilities ​ ​ ​ $ 2,513 ​ $ (2,513) ​ $ - ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2018 (1) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net ​ ​ ​ ​ Gross ​ ​ ​ ​ Recognized ​ ​ ​ ​ Recognized ​ Gross ​ Fair Value Not Designated as ​ ​ ​ Assets/ ​ Amounts ​ Assets/ ASC 815 Hedges Balance Sheet Classification Liabilities Offset Liabilities Derivative assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Commodity contracts - current ​ Derivative assets ​ $ 69,735 ​ $ (1,393) ​ $ 68,342 Total derivative assets ​ ​ ​ $ 69,735 ​ $ (1,393) ​ $ 68,342 Derivative liabilities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Commodity contracts - current ​ Accrued liabilities and other ​ $ 1,393 ​ $ (1,393) ​ $ - Total derivative liabilities ​ ​ ​ $ 1,393 ​ $ (1,393) ​ $ - (1) Because counterparties to the Company’s financial derivative contracts subject to master netting arrangements are lenders under Whiting Oil and Gas’ credit agreement, which eliminates its need to post or receive collateral associated with its derivative positions, columns for cash collateral pledged or received have not been presented in these tables. Contingent Features in Financial Derivative Instruments.

FAIR VALUE MEASUREMENTS

FAIR VALUE MEASUREMENTS	6 Months Ended
	Jun. 30, 2019
FAIR VALUE MEASUREMENTS [Abstract]
FAIR VALUE MEASUREMENTS	8. FAIR VALUE MEASUREMENTS The Company follows FASB ASC Topic 820, Fair Value Measurement and Disclosure ● Level 1: Quoted Prices in Active Markets for Identical Assets – inputs to the valuation methodology are quoted prices (unadjusted) for identical assets or liabilities in active markets. ● Level 2: Significant Other Observable Inputs – inputs to the valuation methodology include quoted prices for similar assets and liabilities in active markets, and inputs that are observable for the asset or liability, either directly or indirectly, for substantially the full term of the financial instrument. ● Level 3: Significant Unobservable Inputs – inputs to the valuation methodology are unobservable and significant to the fair value measurement. A financial instrument’s categorization within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement. The Company’s assessment of the significance of a particular input to the fair value measurement in its entirety requires judgment and considers factors specific to the asset or liability. Cash, cash equivalents, accounts receivable and accounts payable are carried at cost, which approximates their fair value because of the short-term maturity of these instruments. The Company’s credit agreement has a recorded value that approximates its fair value since its variable interest rate is tied to current market rates and the applicable margins represent market rates. The Company’s senior notes are recorded at cost and the convertible senior notes are recorded at fair value at the date of issuance. The following table summarizes the fair values and carrying values of these instruments as of June 30, 2019 and December 31, 2018 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2019 ​ December 31, 2018 ​ ​ Fair ​ Carrying ​ Fair ​ Carrying ​ Value (1) Value (2) Value (1) Value (2) 1.25% Convertible Senior Notes due 2020 ​ $ 545,516 ​ $ 542,716 ​ $ 531,161 ​ $ 530,231 5.75% Senior Notes due 2021 ​ ​ 880,161 ​ ​ 871,203 ​ ​ 829,929 ​ ​ 870,545 6.25% Senior Notes due 2023 ​ ​ 408,296 ​ ​ 405,037 ​ ​ 375,632 ​ ​ 404,659 6.625% Senior Notes due 2026 ​ ​ 960,000 ​ ​ 987,624 ​ ​ 865,000 ​ ​ 986,886 Total ​ $ 2,793,973 ​ $ 2,806,580 ​ $ 2,601,722 ​ $ 2,792,321 (1) Fair values are based on quoted market prices for these debt securities, and such fair values are therefore designated as Level 1 within the valuation hierarchy. (2) Carrying values are presented net of unamortized debt issuance costs and debt discounts or premiums. The Company’s derivative financial instruments are recorded at fair value and include a measure of the Company’s own nonperformance risk or that of its counterparty, as appropriate. The following tables present information about the Company’s financial assets and liabilities measured at fair value on a recurring basis as of June 30, 2019 and December 31, 2018, and indicate the fair value hierarchy of the valuation techniques utilized by the Company to determine such fair values (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total Fair Value ​ Level 1 Level 2 Level 3 June 30, 2019 Financial Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Commodity derivatives – current ​ $ - ​ $ 25,971 ​ $ - ​ $ 25,971 Total financial assets ​ $ - ​ $ 25,971 ​ $ - ​ $ 25,971 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total Fair Value ​ Level 1 Level 2 Level 3 December 31, 2018 Financial Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Commodity derivatives – current ​ $ - ​ $ 68,342 ​ $ - ​ $ 68,342 Total financial assets ​ $ - ​ $ 68,342 ​ $ - ​ $ 68,342 ​ The following methods and assumptions were used to estimate the fair values of the Company’s financial assets and liabilities that are measured on a recurring basis: Commodity Derivatives In addition, the Company had a long-term crude oil sales and delivery contract, whereby it had committed to deliver certain fixed volumes of crude oil produced from its Redtail field in Colorado. Whiting determined that the contract did not meet the “normal purchase normal sale” exclusion, and therefore reflected this contract at fair value in its consolidated financial statements prior to settlement. This commodity derivative was valued based on a probability-weighted income approach which considered various assumptions, including quoted spot prices for commodities, market differentials for crude oil, U.S. Treasury rates and either the Company’s or the counterparty’s nonperformance risk, as appropriate. The assumptions used in the valuation of the crude oil sales and delivery contract included certain market differential metrics that were unobservable during the term of the contract. Such unobservable inputs were significant to the contract valuation methodology, and the contract’s fair value was therefore designated as Level 3 within the valuation hierarchy. On February 1, 2018, Whiting paid $61 million to the counterparty to settle all future minimum volume commitments under this agreement. Accordingly, this derivative was settled in its entirety as of that date. Level 3 Fair Value Measurements — ​ ​ ​ ​ ​ ​ ​ Six Months Ended ​ ​ June 30, 2018 Fair value liability, beginning of period ​ $ (63,278) Unrealized gains on commodity derivative contracts included in earnings (1) ​ ​ 2,242 Settlement of commodity derivative contracts ​ ​ 61,036 Transfers into (out of) Level 3 ​ ​ - Fair value liability, end of period ​ $ - (1) Included in derivative (gain) loss, net in the consolidated statements of operations. Non-recurring Fair Value Measurements — value on an ongoing basis but are subject to fair value adjustments only in certain circumstances. The Company did not recognize any impairment write-downs with respect to its proved property during the reporting periods presented.

REVENUE RECOGNITION

REVENUE RECOGNITION	6 Months Ended
	Jun. 30, 2019
REVENUE RECOGNITION [Abstract]
REVENUE RECOGNITION	9. REVENUE RECOGNITION The Company recognizes revenue in accordance with FASB ASC Topic 606 – Revenue Recognition ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended June 30, ​ Six Months Ended June 30, ​ 2019 ​ ​ 2018 ​ 2019 ​ 2018 OPERATING REVENUES ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Oil sales ​ $ 403,870 ​ ​ $ 482,756 ​ $ 763,324 ​ $ 936,406 NGL and natural gas sales ​ ​ 22,394 ​ ​ ​ 43,647 ​ ​ 52,429 ​ ​ 105,080 Oil, NGL and natural gas sales ​ $ 426,264 ​ ​ $ 526,403 ​ $ 815,753 ​ $ 1,041,486 ​ Whiting receives payment for product sales from one to three months after delivery. At the end of each month when the performance obligation is satisfied, the variable consideration can be reasonably estimated and amounts due from customers are accrued in accounts receivable trade, net in the consolidated balance sheets. As of June 30, 2019 and December 31, 2018, such receivable balances were $157 million and $165 million, respectively. Variances between the Company’s estimated revenue and actual payments are recorded in the month the payment is received, however, differences have been and are insignificant. Accordingly, the variable consideration is not constrained. The Company has elected to utilize the practical expedient in ASC 606 that states the Company is not required to disclose the transaction price allocated to remaining performance obligations if the variable consideration is allocated entirely to a wholly unsatisfied performance obligation. Under the Company’s contracts, each monthly delivery of product represents a separate performance obligation, therefore, future volumes are wholly unsatisfied, and disclosure of the transaction price allocated to remaining performance obligations is not required.

STOCK-BASED COMPENSATION

STOCK-BASED COMPENSATION	6 Months Ended
	Jun. 30, 2019
STOCK-BASED COMPENSATION [Abstract]
STOCK-BASED COMPENSATION	10. STOCK-BASED COMPENSATION Equity Incentive Plan The Company grants service-based RSAs and RSUs to executive officers and employees, which generally vest ratably over a three-year service period. The Company also grants service-based RSAs to directors, which generally vest over a one-year service period. In addition, the Company grants PSAs and PSUs to executive officers that are subject to market-based vesting criteria, which generally vest over a three-year service period. The Company accounts for forfeitures of awards granted under these plans as they occur in determining compensation expense. The Company recognizes compensation expense for all awards subject to market-based vesting conditions regardless of whether it becomes probable that these conditions will be achieved or not, and compensation expense for share-settled awards is not reversed if vesting does not actually occur. During the six months ended June 30, 2019 and 2018, 389,303 and 234,949 shares, respectively, of service-based RSAs and RSUs were granted to executive officers and directors under the 2013 Equity Plan. The Company determines compensation expense for these share-settled awards using their fair value at the grant date, which is based on the closing bid price of the Company’s common stock on such date. The weighted average grant date fair value of service-based RSAs and RSUs was $27.97 per share and $31.92 per share for the six months ended June 30, 2019 and 2018, respectively. During the six months ended June 30, 2018, 308,432 shares of service-based RSUs were granted to employees under the 2013 Equity Plan. These awards will be settled in cash and are recorded as a liability in the consolidated balance sheets. The Company determines compensation expense for cash-settled RSUs using the fair value at the end of each reporting period, which is based on the closing bid price of the Company’s common stock on such date. During the six months ended June 30, 2019 and 2018, 317,512 and 215,898, respectively, of PSAs and PSUs subject to certain market-based vesting criteria were granted to executive officers under the 2013 Equity Plan. These market-based awards cliff vest on the third anniversary of the grant date, and the number of shares that will vest at the end of that three-year performance period is determined based on the rank of Whiting’s cumulative stockholder return compared to the stockholder return of a peer group of companies on each anniversary of the grant date over the three-year performance period. The number of awards earned could range from zero up to two times the number of shares initially granted. However, awards earned up to the target shares granted (or 100%) will be settled in shares, while awards earned in excess of the target shares granted will be settled in cash. The cash-settled component of such awards is recorded as a liability in the consolidated balance sheets and will be remeasured at fair value using a Monte Carlo valuation model at the end of each reporting period. For awards subject to market conditions, the grant date fair value is estimated using a Monte Carlo valuation model. The Monte Carlo model is based on random projections of stock price paths and must be repeated numerous times to achieve a probabilistic assessment. Expected volatility is calculated based on the historical volatility and implied volatility of Whiting’s common stock, and the risk-free interest rate is based on U.S. Treasury yield curve rates with maturities consistent with the three-year vesting period. The key assumptions used in valuing these market-based awards were as follows: ​ ​ ​ ​ ​ ​ ​ 2019 2018 Number of simulations 2,500,000 2,500,000 Expected volatility 72.95% ​ 72.80% Risk-free interest rate 2.60% ​ 2.12% Dividend yield — — ​ The weighted average grant date fair value of the market-based awards that will be settled in shares, as determined by the Monte Carlo valuation model, was $25.97 per share and $27.28 per share in 2019 and 2018, respectively. The following table shows a summary of the Company’s service-based and market-based awards activity for the six months ended June 30, 2019: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Number of Awards ​ Weighted Average ​ ​ Service ‑ Based ​ Market-Based ​ Grant Date ​ RSAs & RSUs PSAs & PSUs Fair Value Nonvested awards, January 1 554,527 503,696 ​ $ 34.94 Granted 389,303 317,512 ​ 27.07 Vested (335,911) (98,581) ​ 32.76 Forfeited (5,955) (111,199) ​ 28.37 Nonvested awards, June 30 601,964 611,428 ​ $ 31.77 ​ There was no significant stock option activity during the six months ended June 30, 2019 and 2018. Total stock compensation expense recognized for restricted stock was $4 million and $5 million for the three months ended June 30, 2019 and 2018, respectively, and $10 million and $12 million for the six months ended June 30, 2019 and 2018, respectively.

INCOME TAXES

INCOME TAXES	6 Months Ended
	Jun. 30, 2019
INCOME TAXES [Abstract]
INCOME TAXES	11. INCOME TAXES Income tax expense during interim periods is based on applying an estimated annual effective income tax rate to year-to-date income, plus any significant unusual or infrequently occurring items which are recorded in the interim period. The provision for income taxes for the three and six months ended June 30, 2019 and 2018 differs from the amount that would be provided by applying the statutory U.S. federal income tax rate of 21% to pre-tax income primarily due to (i) the recognition of a full valuation allowance during the three months ended June 30, 2019 and (ii) for the three and six months ended June 30, 2018, a full valuation allowance was already in effect, which reduced the Company’s net tax expense to zero. In assessing the realizability of deferred tax assets (“DTAs”), management considers whether it is more likely than not that some portion, or all, of the Company’s DTAs will not be realized. In making such determination, the Company considers all available positive and negative evidence, including future reversals of temporary differences, tax-planning strategies and projected future taxable income and results of operations. If the Company concludes that it is more likely than not that some portion, or all, of its DTAs will not be realized, the tax asset is reduced by a valuation allowance. The Company assesses the appropriateness of its valuation allowance on a quarterly basis. At December 31, 2018, the Company had a valuation allowance totaling $152 million on a portion of its net DTAs, and as of June 30, 2019, the Company had a full valuation allowance on its DTAs. The computation of the annual estimated effective tax rate at each interim period requires certain estimates and significant judgment including, but not limited to, the expected operating income for the year, projections of the proportion of income earned and taxed in various jurisdictions, permanent and temporary differences, and the likelihood of recovering deferred tax assets generated in the current year. The accounting estimates used to compute the provision for income taxes may change as new events occur, more experience is obtained, additional information becomes known or as the tax environment changes.

EARNINGS PER SHARE

EARNINGS PER SHARE	6 Months Ended
	Jun. 30, 2019
EARNINGS PER SHARE [Abstract]
EARNINGS PER SHARE	12. EARNINGS PER SHARE The reconciliations between basic and diluted earnings (loss) per share are as follows (in thousands, except per share data): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended June 30, ​ Six Months Ended June 30, ​ 2019 2018 2019 2018 Basic Earnings (Loss) Per Share ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net income (loss) ​ $ (5,687) ​ $ 2,120 ​ $ (74,612) ​ $ 17,132 Weighted average shares outstanding, basic ​ ​ 91,286 ​ ​ 90,940 ​ ​ 91,261 ​ ​ 90,916 Earnings (loss) per common share, basic ​ $ (0.06) ​ $ 0.02 ​ $ (0.82) ​ $ 0.19 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Diluted Earnings (Loss) Per Share ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net income (loss) ​ $ (5,687) ​ $ 2,120 ​ $ (74,612) ​ $ 17,132 Weighted average shares outstanding, basic ​ ​ 91,286 ​ ​ 90,940 ​ ​ 91,261 ​ ​ 90,916 Service-based awards, market-based awards and stock options ​ ​ - ​ ​ 929 ​ ​ - ​ ​ 905 Weighted average shares outstanding, diluted ​ ​ 91,286 ​ ​ 91,869 ​ ​ 91,261 ​ ​ 91,821 Earnings (loss) per common share, diluted ​ $ (0.06) ​ $ 0.02 ​ $ (0.82) ​ $ 0.19 ​ During the three months ended June 30, 2019, the Company had a net loss and therefore the diluted earnings per share calculation for that period excludes the anti-dilutive effect of 182,583 shares of service-based awards and 96,241 shares of market-based awards. In addition, the diluted earnings per share calculation for the three months ended June 30, 2019 excludes the effect of 46,396 common shares for stock options that were out-of-the-money as of June 30, 2019. During the three months ended June 30, 2018, the diluted earnings per share calculation excludes the effect of 112,574 common shares for stock options that were out-of-the-money as of June 30, 2018. During the six months ended June 30, 2019, the Company had a net loss and therefore the diluted earnings per share calculation for that period excludes the anti-dilutive effect of 293,505 shares of service-based awards and 206,475 shares of market-based awards. In addition, the diluted earnings per share calculation for the six months ended June 30, 2019 excludes the effect of 46,502 common shares for stock options that were out-of-the money as of June 30, 2019. During the six months ended June 30, 2018, the diluted earnings per share calculation excludes the effect of 116,552 common shares for stock options that were out-of-the-money. Refer to the “Stock-Based Compensation” footnote for further information on the Company’s service-based awards, market-based awards and stock options. As discussed in the “Long-Term Debt” footnote, the Company has the option to settle conversions of the 2020 Convertible Senior Notes with cash, shares of common stock or any combination thereof. Based on the current conversion price, the entire outstanding principal amount of the 2020 Convertible Senior Notes as of June 30, 2019 would be convertible into approximately 3.6 million shares of the Company’s common stock. However, the Company’s intent is to settle the principal amount of the notes in cash upon conversion. As a result, only the amount by which the conversion value exceeds the aggregate principal amount of the notes (the “conversion spread”) is considered in the diluted earnings per share computation under the treasury stock method. As of June 30, 2019 and 2018, the conversion value did not exceed the principal amount of the notes. Accordingly, there was no impact to diluted earnings per share or the related disclosures for those periods.

SUBSEQUENT EVENT

SUBSEQUENT EVENT	6 Months Ended
	Jun. 30, 2019
SUBSEQUENT EVENT [Abstract]
SUBSEQUENT EVENT	13. SUBSEQUENT EVENTS On July 2, 2019, the Company entered into agreements for the sale of its interests in 58 non-operated, producing oil and gas wells located in Richland County, Montana and Mountrail and Williams counties of North Dakota for aggregate sales proceeds of $26 million (before closing adjustments). Upon executing the sale agreements, the Company received a $3 million deposit. This transaction is expected to close during the third quarter of 2019. On July 29, 2019, the Company completed the divestiture of its interests in 137 non-operated, producing oil and gas wells located in the McKenzie, Mountrail and Williams counties of North Dakota for aggregate sales proceeds of $27 million (before closing adjustments).

BASIS OF PRESENTATION (Policies

BASIS OF PRESENTATION (Policies)	6 Months Ended
	Jun. 30, 2019
BASIS OF PRESENTATION [Abstract]
Condensed Consolidated Financial Statements	Condensed Consolidated Financial Statements
Reclassifications	Reclassifications —
Adopted and Recently Issued Accounting Pronouncements	Adopted and Recently Issued Accounting Pronouncements Leases Leases

OIL AND GAS PROPERTIES (Tables)

OIL AND GAS PROPERTIES (Tables)	6 Months Ended
	Jun. 30, 2019
OIL AND GAS PROPERTIES [Abstract]
Net capitalized costs related to oil and gas producing activities	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ 2019 2018 Costs of completed wells and facilities ​ $ 9,546,167 ​ $ 9,182,384 Proved leasehold costs ​ ​ 2,734,887 ​ ​ 2,729,593 Wells and facilities in progress ​ ​ 228,164 ​ ​ 160,995 Unproved leasehold costs ​ ​ 109,019 ​ ​ 122,687 Total oil and gas properties, successful efforts method ​ ​ 12,618,237 ​ ​ 12,195,659 Accumulated depletion ​ ​ (5,313,661) ​ ​ (4,937,579) Oil and gas properties, net ​ $ 7,304,576 ​ $ 7,258,080 ​

ACQUISITIONS AND DIVESTITURES (

ACQUISITIONS AND DIVESTITURES (Tables)	6 Months Ended
	Jun. 30, 2019
ACQUISITIONS AND DIVESTITURES [Abstract]
Schedule of purchase price allocation	​ ​ ​ ​ ​ Cash consideration ​ $ 122,861 ​ ​ ​ ​ Fair value of assets acquired: ​ ​ ​ Accounts receivable trade, net ​ $ 30 Prepaid expenses and other ​ ​ 43 Oil and gas properties, successful efforts method: ​ ​ ​ Proved oil and gas properties ​ ​ 106,860 Unproved oil and gas properties ​ ​ 21,769 Total fair value of assets acquired ​ ​ 128,702 ​ ​ ​ ​ Fair value of liabilities assumed: ​ ​ ​ Revenue and royalties payable ​ ​ 3,309 Asset retirement obligations ​ ​ 2,532 Total fair value of liabilities assumed ​ ​ 5,841 ​ ​ ​ ​ Total fair value of assets and liabilities acquired ​ $ 122,861

LEASES (Tables)

LEASES (Tables)	6 Months Ended
	Jun. 30, 2019
LEASES [Abstract]
Summary of lease balance sheet information	Supplemental balance sheet information for the Company’s leases as of June 30, 2019 consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Leases ​ Balance Sheet Classification ​ June 30, 2019 ​ ​ ​ ​ ​ ​ Operating Leases ​ ​ ​ ​ ​ Operating lease ROU assets ​ Other long-term assets ​ $ 18,634 Accumulated depreciation ​ Other long-term assets ​ ​ (5,373) Operating lease ROU assets, net ​ ​ ​ $ 13,261 ​ ​ ​ ​ ​ ​ Short-term operating lease obligations ​ Accrued liabilities and other ​ $ 6,335 Long-term operating lease obligations ​ Operating lease obligations ​ ​ 13,000 Total operating lease obligations ​ ​ ​ $ 19,335 ​ ​ ​ ​ ​ ​ Finance Leases ​ ​ ​ ​ ​ Finance lease ROU assets ​ Other property and equipment ​ $ 34,237 Accumulated depreciation ​ Accumulated depreciation, depletion and amortization ​ ​ (14,424) Finance lease ROU assets, net ​ ​ ​ $ 19,813 ​ ​ ​ ​ ​ ​ Short-term finance lease obligations ​ Accrued liabilities and other ​ $ 5,003 Long-term finance lease obligations ​ Other long-term liabilities ​ ​ 17,170 Total finance lease obligations ​ ​ ​ $ 22,173 ​ The Company’s leases have terms of less than one year to 11 years. Most of the Company’s leases do not state or imply a discount rate. Accordingly, the Company uses its incremental borrowing rate based on information available at lease commencement to determine the present value of the lease payments. Information regarding the Company’s lease terms and discount rates as of June 30, 2019 is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted Average Remaining Lease Term ​ ​ ​ ​ ​ Operating leases ​ ​ ​ ​ 7 years Finance leases ​ ​ ​ ​ 5 years ​ ​ ​ ​ ​ ​ Weighted Average Discount Rate ​ ​ ​ ​ ​ Operating leases ​ ​ ​ ​ 4.9% Finance leases ​ ​ ​ ​ 9.0% ​
Summary of lease cost	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ June 30, 2019 ​ June 30, 2019 Operating lease cost ​ $ 2,883 ​ $ 5,753 ​ ​ ​ ​ ​ ​ ​ Finance lease cost: ​ ​ ​ ​ ​ ​ Amortization of ROU assets ​ $ 1,381 ​ $ 2,778 Interest on lease liabilities ​ ​ 504 ​ ​ 1,024 Total finance lease cost ​ $ 1,885 ​ $ 3,802 ​ ​ ​ ​ ​ ​ ​ Short-term lease payments ​ $ 220,741 ​ $ 345,063 Variable lease payments ​ $ 5,840 ​ $ 10,775
Summary of lease cash flow information	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ June 30, 2019 ​ June 30, 2019 Cash paid for amounts included in the measurement of lease liabilities: ​ ​ ​ ​ ​ ​ Operating cash flows from operating leases ​ $ 2,637 ​ $ 5,415 Operating cash flows from finance leases ​ $ 503 ​ $ 1,021 Financing cash flows from finance leases ​ $ 1,258 ​ $ 2,522 ​ ​ ​ ​ ​ ​ ​ ROU assets obtained in exchange for new operating lease obligations ​ $ 2 ​ $ 11 ROU assets obtained in exchange for new finance lease obligations ​ $ 599 ​ $ 1,336
Summary of operating lease obligations	The Company’s lease obligations as of June 30, 2019 will mature as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ending December 31, ​ Operating Leases ​ Finance Leases 2019 ​ $ 4,518 ​ $ 3,499 2020 ​ ​ 4,001 ​ ​ 6,399 2021 ​ ​ 1,891 ​ ​ 5,091 2022 ​ ​ 1,857 ​ ​ 4,014 2023 ​ ​ 1,608 ​ ​ 3,348 Remaining ​ ​ 9,232 ​ ​ 5,766 Total lease payments ​ $ 23,107 ​ $ 28,117 Less imputed interest ​ ​ (3,772) ​ ​ (5,944) Total discounted lease payments ​ $ 19,335 ​ $ 22,173
Summary of finance lease obligations	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ending December 31, ​ Operating Leases ​ Finance Leases 2019 ​ $ 4,518 ​ $ 3,499 2020 ​ ​ 4,001 ​ ​ 6,399 2021 ​ ​ 1,891 ​ ​ 5,091 2022 ​ ​ 1,857 ​ ​ 4,014 2023 ​ ​ 1,608 ​ ​ 3,348 Remaining ​ ​ 9,232 ​ ​ 5,766 Total lease payments ​ $ 23,107 ​ $ 28,117 Less imputed interest ​ ​ (3,772) ​ ​ (5,944) Total discounted lease payments ​ $ 19,335 ​ $ 22,173
Minimum future payments under non-cancelable operating leases and unconditional purchase obligations	As of December 31, 2018, minimum future contractual payments for long-term leases under the scope of ASC 840 are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Pipeline ​ Automobile and ​ ​ Real Estate ​ Transportation ​ Equipment Year ending December 31, ​ Leases ​ Agreement ​ Leases 2019 ​ $ 7,407 ​ $ 3,180 ​ $ 4,216 2020 ​ ​ 4,770 ​ ​ 3,180 ​ ​ 3,422 2021 ​ ​ 4,066 ​ ​ 3,180 ​ ​ 1,678 2022 ​ ​ 4,188 ​ ​ 3,180 ​ ​ 488 2023 ​ ​ 4,017 ​ ​ 3,180 ​ ​ 35 Remaining ​ ​ 25,140 ​ ​ 5,565 ​ ​ - Total lease payments ​ $ 49,588 ​ $ 21,465 ​ $ 9,839 ​

LONG-TERM DEBT (Tables)

LONG-TERM DEBT (Tables)	6 Months Ended
	Jun. 30, 2019
LONG-TERM DEBT [Abstract]
Schedule of long-term debt	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ 2019 2018 Credit agreement ​ $ 40,000 ​ $ - 1.25% Convertible Senior Notes due 2020 ​ ​ 562,075 ​ ​ 562,075 5.75% Senior Notes due 2021 ​ ​ 873,609 ​ ​ 873,609 6.25% Senior Notes due 2023 ​ ​ 408,296 ​ ​ 408,296 6.625% Senior Notes due 2026 ​ ​ 1,000,000 ​ ​ 1,000,000 Total principal ​ ​ 2,883,980 ​ ​ 2,843,980 Unamortized debt discounts and premiums ​ ​ (17,550) ​ ​ (28,994) Unamortized debt issuance costs on notes ​ ​ (19,850) ​ ​ (22,665) Total debt ​ ​ 2,846,580 ​ ​ 2,792,321 Less current portion of long-term debt ​ ​ (542,716) ​ ​ - Total long-term debt ​ $ 2,303,864 ​ $ 2,792,321
Summary of margin rates and commitment fees	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Applicable ​ Applicable ​ ​ ​ ​ Margin for Base ​ Margin for ​ Commitment Ratio of Outstanding Borrowings to Borrowing Base Rate Loans Eurodollar Loans Fee Less than 0.25 to 1.0 ​ 0.50% ​ 1.50% ​ 0.375% Greater than or equal to 0.25 to 1.0 but less than 0.50 to 1.0 ​ 0.75% ​ 1.75% ​ 0.375% Greater than or equal to 0.50 to 1.0 but less than 0.75 to 1.0 ​ 1.00% ​ 2.00% ​ 0.50% Greater than or equal to 0.75 to 1.0 but less than 0.90 to 1.0 ​ 1.25% ​ 2.25% ​ 0.50% Greater than or equal to 0.90 to 1.0 ​ 1.50% ​ 2.50% ​ 0.50%
Summary of senior notes and convertible senior notes	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2020 ​ ​ ​ ​ ​ Convertible ​ 2021 ​ 2023 ​ 2026 ​ ​ Senior Notes ​ Senior Notes ​ Senior Notes ​ Senior Notes Outstanding principal (in thousands) ​ $ 562,075 ​ $ 873,609 ​ $ 408,296 ​ $ 1,000,000 Interest rate ​ 1.25% ​ 5.75% ​ 6.25% ​ 6.625% Maturity date ​ Apr 1, 2020 ​ Mar 15, 2021 ​ Apr 1, 2023 ​ Jan 15, 2026 Interest payment dates ​ Apr 1, Oct 1 ​ Mar 15, Sep 15 ​ Apr 1, Oct 1 ​ Jan 15, Jul 15 Make-whole redemption date (1) ​ N/A (2) ​ Dec 15, 2020 ​ Jan 1, 2023 ​ Oct 15, 2025 (1) On or after these dates, the Company may redeem the applicable series of notes, in whole or in part, at a redemption price equal to 100% of the principal amount redeemed, together with accrued and unpaid interest up to the redemption date. At any time prior to these dates, the Company may redeem the notes at a redemption price that includes an applicable premium as defined in the indentures to such notes. (2) The indenture governing the 1.25% Convertible Senior Notes due 2020 does not allow for optional redemption by the Company prior to the maturity date.
Schedule of convertible senior notes	The 2020 Convertible Senior Notes consisted of the following at June 30, 2019 and December 31, 2018 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ 2019 2018 Liability component ​ ​ ​ ​ ​ ​ Principal ​ $ 562,075 ​ $ 562,075 Less: unamortized note discount ​ ​ (17,950) ​ ​ (29,504) Less: unamortized debt issuance costs ​ ​ (1,409) ​ ​ (2,340) Net carrying value ​ $ 542,716 ​ $ 530,231 Equity component (1) ​ $ 136,522 ​ $ 136,522 (1) Recorded in additional paid-in capital, net of $5 million of issuance costs and $50 million of deferred taxes.
Interest expense on convertible senior notes	The following table presents the interest expense recognized on the 2020 Convertible Senior Notes related to the stated interest rate and amortization of the debt discount for the three and six months ended June 30, 2019 and 2018 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ June 30, ​ June 30, ​ ​ 2019 ​ 2018 ​ 2019 ​ 2018 Interest expense on 2020 Convertible Senior Notes ​ $ 7,574 ​ $ 7,258 ​ $ 15,068 ​ $ 14,439

ASSET RETIREMENT OBLIGATIONS (T

ASSET RETIREMENT OBLIGATIONS (Tables)	6 Months Ended
	Jun. 30, 2019
ASSET RETIREMENT OBLIGATIONS [Abstract]
Schedule of reconciliation of the Company's asset retirement obligations	​ ​ ​ ​ ​ Asset retirement obligation at January 1, 2019 ​ $ 135,834 Additional liability incurred ​ ​ 1,982 Revisions to estimated cash flows ​ ​ (7,511) Accretion expense ​ ​ 5,819 Obligations on sold properties ​ ​ (310) Liabilities settled ​ ​ 167 Asset retirement obligation at June 30, 2019 ​ $ 135,981 ​

DERIVATIVE FINANCIAL INSTRUME_2

DERIVATIVE FINANCIAL INSTRUMENTS (Tables)	6 Months Ended
	Jun. 30, 2019
DERIVATIVE FINANCIAL INSTRUMENTS [Abstract]
Derivative instruments	​ ​ ​ ​ ​ ​ ​ ​ Derivative ​ ​ ​ Contracted Crude ​ Weighted Average NYMEX Price Instrument Period Oil Volumes (Bbl) for Crude Oil (per Bbl) Collars (1) ​ Jul - Dec 2019 ​ 5,400,000 ​ $52.56 - $75.17 ​ ​ Jan - Jun 2020 ​ 728,000 ​ $55.00 - $67.33 Swaps (1) ​ Jul - Dec 2019 ​ 3,300,000 ​ $61.43 ​ ​ Jan - Jun 2020 ​ 2,184,000 ​ $58.88 ​ ​ Total ​ 11,612,000 ​ ​ (1) Subsequent to June 30, 2019, the Company entered into additional swap contracts for 250,000 Bbl of crude oil volumes for the remainder of 2019.
Schedule of effects of commodity derivative instruments	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (Gain) Loss Recognized in Income Not Designated as ​ Statement of Operations ​ Three Months Ended June 30, ASC 815 Hedges ​ Classification ​ 2019 ​ 2018 Commodity contracts ​ Derivative (gain) loss, net ​ $ (24,877) ​ $ 103,483 Total ​ ​ ​ $ (24,877) ​ $ 103,483 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Loss Recognized in Income Not Designated as ​ Statement of Operations ​ Six Months Ended June 30, ASC 815 Hedges Classification 2019 2018 Commodity contracts ​ Derivative (gain) loss, net ​ $ 38,028 ​ $ 156,147 Total ​ ​ ​ $ 38,028 ​ $ 156,147
Location and fair value of derivative instruments	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2019 (1) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net ​ ​ ​ ​ Gross ​ ​ ​ ​ Recognized ​ ​ ​ ​ Recognized ​ Gross ​ Fair Value Not Designated as ​ ​ ​ Assets/ ​ Amounts ​ Assets/ ASC 815 Hedges Balance Sheet Classification Liabilities Offset Liabilities Derivative assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Commodity contracts - current ​ Derivative assets ​ $ 28,484 ​ $ (2,513) ​ $ 25,971 Total derivative assets ​ ​ ​ $ 28,484 ​ $ (2,513) ​ $ 25,971 Derivative liabilities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Commodity contracts - current ​ Accrued liabilities and other ​ $ 2,513 ​ $ (2,513) ​ $ - Total derivative liabilities ​ ​ ​ $ 2,513 ​ $ (2,513) ​ $ - ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2018 (1) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net ​ ​ ​ ​ Gross ​ ​ ​ ​ Recognized ​ ​ ​ ​ Recognized ​ Gross ​ Fair Value Not Designated as ​ ​ ​ Assets/ ​ Amounts ​ Assets/ ASC 815 Hedges Balance Sheet Classification Liabilities Offset Liabilities Derivative assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Commodity contracts - current ​ Derivative assets ​ $ 69,735 ​ $ (1,393) ​ $ 68,342 Total derivative assets ​ ​ ​ $ 69,735 ​ $ (1,393) ​ $ 68,342 Derivative liabilities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Commodity contracts - current ​ Accrued liabilities and other ​ $ 1,393 ​ $ (1,393) ​ $ - Total derivative liabilities ​ ​ ​ $ 1,393 ​ $ (1,393) ​ $ - (1) Because counterparties to the Company’s financial derivative contracts subject to master netting arrangements are lenders under Whiting Oil and Gas’ credit agreement, which eliminates its need to post or receive collateral associated with its derivative positions, columns for cash collateral pledged or received have not been presented in these tables.

FAIR VALUE MEASUREMENTS (Tables

FAIR VALUE MEASUREMENTS (Tables)	6 Months Ended
	Jun. 30, 2019
FAIR VALUE MEASUREMENTS [Abstract]
Summary of the fair values and carrying value of debt instruments	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2019 ​ December 31, 2018 ​ ​ Fair ​ Carrying ​ Fair ​ Carrying ​ Value (1) Value (2) Value (1) Value (2) 1.25% Convertible Senior Notes due 2020 ​ $ 545,516 ​ $ 542,716 ​ $ 531,161 ​ $ 530,231 5.75% Senior Notes due 2021 ​ ​ 880,161 ​ ​ 871,203 ​ ​ 829,929 ​ ​ 870,545 6.25% Senior Notes due 2023 ​ ​ 408,296 ​ ​ 405,037 ​ ​ 375,632 ​ ​ 404,659 6.625% Senior Notes due 2026 ​ ​ 960,000 ​ ​ 987,624 ​ ​ 865,000 ​ ​ 986,886 Total ​ $ 2,793,973 ​ $ 2,806,580 ​ $ 2,601,722 ​ $ 2,792,321 (1) Fair values are based on quoted market prices for these debt securities, and such fair values are therefore designated as Level 1 within the valuation hierarchy. (2) Carrying values are presented net of unamortized debt issuance costs and debt discounts or premiums.
Fair value assets and liabilities measured on a recurring basis	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total Fair Value ​ Level 1 Level 2 Level 3 June 30, 2019 Financial Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Commodity derivatives – current ​ $ - ​ $ 25,971 ​ $ - ​ $ 25,971 Total financial assets ​ $ - ​ $ 25,971 ​ $ - ​ $ 25,971 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total Fair Value ​ Level 1 Level 2 Level 3 December 31, 2018 Financial Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Commodity derivatives – current ​ $ - ​ $ 68,342 ​ $ - ​ $ 68,342 Total financial assets ​ $ - ​ $ 68,342 ​ $ - ​ $ 68,342
Reconciliation of changes in the fair value of financial assets (liabilities) designated as Level 3 in the valuation hierarchy	​ ​ ​ ​ ​ ​ ​ Six Months Ended ​ ​ June 30, 2018 Fair value liability, beginning of period ​ $ (63,278) Unrealized gains on commodity derivative contracts included in earnings (1) ​ ​ 2,242 Settlement of commodity derivative contracts ​ ​ 61,036 Transfers into (out of) Level 3 ​ ​ - Fair value liability, end of period ​ $ - (1) Included in derivative (gain) loss, net in the consolidated statements of operations.

REVENUE RECOGNITION (Tables)

REVENUE RECOGNITION (Tables)	6 Months Ended
	Jun. 30, 2019
REVENUE RECOGNITION [Abstract]
Summary of revenue disaggregation	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended June 30, ​ Six Months Ended June 30, ​ 2019 ​ ​ 2018 ​ 2019 ​ 2018 OPERATING REVENUES ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Oil sales ​ $ 403,870 ​ ​ $ 482,756 ​ $ 763,324 ​ $ 936,406 NGL and natural gas sales ​ ​ 22,394 ​ ​ ​ 43,647 ​ ​ 52,429 ​ ​ 105,080 Oil, NGL and natural gas sales ​ $ 426,264 ​ ​ $ 526,403 ​ $ 815,753 ​ $ 1,041,486

STOCK-BASED COMPENSATION (Table

STOCK-BASED COMPENSATION (Tables)	6 Months Ended
	Jun. 30, 2019
STOCK-BASED COMPENSATION [Abstract]
Assumption for valuing market based restricted shares	​ ​ ​ ​ ​ ​ ​ 2019 2018 Number of simulations 2,500,000 2,500,000 Expected volatility 72.95% ​ 72.80% Risk-free interest rate 2.60% ​ 2.12% Dividend yield — —
Summary of nonvested shares	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Number of Awards ​ Weighted Average ​ ​ Service ‑ Based ​ Market-Based ​ Grant Date ​ RSAs & RSUs PSAs & PSUs Fair Value Nonvested awards, January 1 554,527 503,696 ​ $ 34.94 Granted 389,303 317,512 ​ 27.07 Vested (335,911) (98,581) ​ 32.76 Forfeited (5,955) (111,199) ​ 28.37 Nonvested awards, June 30 601,964 611,428 ​ $ 31.77

EARNINGS PER SHARE (Tables)

EARNINGS PER SHARE (Tables)	6 Months Ended
	Jun. 30, 2019
EARNINGS PER SHARE [Abstract]
Reconciliations between basic and diluted earnings per share	The reconciliations between basic and diluted earnings (loss) per share are as follows (in thousands, except per share data): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended June 30, ​ Six Months Ended June 30, ​ 2019 2018 2019 2018 Basic Earnings (Loss) Per Share ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net income (loss) ​ $ (5,687) ​ $ 2,120 ​ $ (74,612) ​ $ 17,132 Weighted average shares outstanding, basic ​ ​ 91,286 ​ ​ 90,940 ​ ​ 91,261 ​ ​ 90,916 Earnings (loss) per common share, basic ​ $ (0.06) ​ $ 0.02 ​ $ (0.82) ​ $ 0.19 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Diluted Earnings (Loss) Per Share ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net income (loss) ​ $ (5,687) ​ $ 2,120 ​ $ (74,612) ​ $ 17,132 Weighted average shares outstanding, basic ​ ​ 91,286 ​ ​ 90,940 ​ ​ 91,261 ​ ​ 90,916 Service-based awards, market-based awards and stock options ​ ​ - ​ ​ 929 ​ ​ - ​ ​ 905 Weighted average shares outstanding, diluted ​ ​ 91,286 ​ ​ 91,869 ​ ​ 91,261 ​ ​ 91,821 Earnings (loss) per common share, diluted ​ $ (0.06) ​ $ 0.02 ​ $ (0.82) ​ $ 0.19

OIL AND GAS PROPERTIES (Details

OIL AND GAS PROPERTIES (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
OIL AND GAS PROPERTIES [Abstract]
Costs of completed wells and facilities	$ 9,546,167	$ 9,182,384
Proved leasehold costs	2,734,887	2,729,593
Wells and facilities in progress	228,164	160,995
Unproved leasehold costs	109,019	122,687
Total oil and gas properties, successful efforts method	12,618,237	12,195,659
Accumulated depletion	(5,313,661)	(4,937,579)
Oil and gas properties, net	$ 7,304,576	$ 7,258,080

ACQUISITIONS AND DIVESTITURES_2

ACQUISITIONS AND DIVESTITURES (Acquisition) (Details) $ in Thousands	Jul. 31, 2018USD ($)aitem	Jun. 30, 2019USD ($)	Jun. 30, 2018USD ($)
Business Acquisition [Line Items]
Cash consideration		$ 4,507	$ 8,529
Richland and McKenzie Counties [Member]
Business Acquisition [Line Items]
Aggregate purchase price	$ 130,000
Net acquisition area (in acres) | a	54,800
Number of wells acquired | item	117
Cash consideration	$ 122,861
Fair value of assets acquired:
Accounts receivable trade, net	30
Prepaid expenses and other	43
Oil and gas properties, successful efforts method:
Proved oil and gas properties	106,860
Unproved oil and gas properties	21,769
Total fair value of assets acquired	128,702
Fair value of liabilities assumed:
Revenue and royalties payable	3,309
Asset retirement obligations	2,532
Total fair value of liabilities assumed	5,841
Total fair value of assets and liabilities acquired	$ 122,861

LEASES (Details)

LEASES (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2019	Jan. 01, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Lease, Practical Expedients, Package [true false]	true
Accounting Standards Update 2016-02 [Member] | Restatement Adjustment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total leased assets		$ 30
Total lease liabilities		$ 36

LEASES (Balance Sheet and Terms

LEASES (Balance Sheet and Terms) (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2019USD ($)
Operating Leases
Operating lease ROU assets	$ 18,634
Operating lease, Accumulated depreciation	(5,373)
Operating lease ROU assets, net	$ 13,261
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Other Assets, Noncurrent
Short-term operating lease obligations	$ 6,335
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	Other Liabilities, Current
Long-term operating lease obligations	$ 13,000
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Long-term operating lease obligations
Total operating lease obligations	$ 19,335
Finance Leases
Finance lease ROU assets	34,237
Finance lease, Accumulated depreciation	(14,424)
Finance lease ROU assets, net	$ 19,813
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Property, Plant and Equipment, Net
Short-term finance lease obligations	$ 5,003
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]	Other Liabilities, Current
Long-term finance lease obligations	$ 17,170
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Other Liabilities, Noncurrent
Total finance lease obligations	$ 22,173
Weighted Average Remaining Lease Term, Operating lease	7 years
Weighted Average Remaining Lease Term, Finance lease	5 years
Weighted Average Discount Rate, Operating lease (as a percent)	4.90%
Weighted Average Discount Rate, Finance lease (as a percent)	9.00%
Minimum [Member]
Finance Leases
Lease term	1 year
Maximum [Member]
Finance Leases
Lease term	11 years

LEASES (Lease cost) (Details)

LEASES (Lease cost) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019
LEASES [Abstract]
Operating lease cost	$ 2,883	$ 5,753
Amortization of ROU assets	1,381	2,778
Interest on lease liabilities	504	1,024
Total finance lease cost	1,885	3,802
Short-term lease payments	220,741	345,063
Variable lease payments	$ 5,840	$ 10,775

LEASES (Cash flow) (Details)

LEASES (Cash flow) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019
LEASES [Abstract]
Operating cash flows from operating leases	$ 2,637	$ 5,415
Operating cash flows from finance leases	503	1,021
Financing cash flows from finance leases	1,258	2,522
ROU assets obtained in exchange for new operating lease obligations	2	11
ROU assets obtained in exchange for new financing lease obligations	$ 599	$ 1,336

LEASES (Obligations) (Details)

LEASES (Obligations) (Details) $ in Thousands	Jun. 30, 2019USD ($)
Operating Leases
2019	$ 4,518
2020	4,001
2021	1,891
2022	1,857
2023	1,608
Remaining	9,232
Total lease payments	23,107
Less imputed interest	(3,772)
Total operating lease obligations	19,335
Finance Leases
2019	3,499
2020	6,399
2021	5,091
2022	4,014
2023	3,348
Remaining	5,766
Total lease payments	28,117
Less imputed interest	(5,944)
Total finance lease obligations	22,173
Operating leases not yet commenced	$ 35,000
Operating lease not yet commenced term	10 years

LEASES (ASC 840 Obligations) (D

LEASES (ASC 840 Obligations) (Details) $ in Thousands	Dec. 31, 2018USD ($)
Real Estate Leases [Member]
Minimum future contractual payments
2019	$ 7,407
2020	4,770
2021	4,066
2022	4,188
2023	4,017
Remaining	25,140
Total	49,588
Pipeline Transportation Agreements [Member]
Minimum future contractual payments
2019	3,180
2020	3,180
2021	3,180
2022	3,180
2023	3,180
Remaining	5,565
Total	21,465
Automobile and Equipment Leases [Member]
Minimum future contractual payments
2019	4,216
2020	3,422
2021	1,678
2022	488
2023	35
Total	$ 9,839

LONG-TERM DEBT (Schedule of lon

LONG-TERM DEBT (Schedule of long-term debt) (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2015	Sep. 30, 2013
Debt Instrument [Line Items]
Total principal	$ 2,883,980	$ 2,843,980
Unamortized debt discounts and premiums	(17,550)	(28,994)
Unamortized debt issuance costs on notes	(19,850)	(22,665)
Total debt	2,846,580	2,792,321
Less current portion of long-term debt	(542,716)
Total long-term debt	2,303,864	2,792,321
Credit Agreement [Member]
Debt Instrument [Line Items]
Total principal	$ 40,000
5.0% Senior Notes due 2019 [Member]
Debt Instrument [Line Items]
Total principal			$ 0
Interest rate on debt instrument (as a percent)	5.00%					5.00%
1.25% Convertible Senior Notes due 2020 [Member]
Debt Instrument [Line Items]
Total principal	$ 562,075	562,075
Unamortized debt issuance costs on notes	$ (1,409)	(2,340)			$ (25,000)
Interest rate on debt instrument (as a percent)	1.25%				1.25%
5.75% Senior Notes due 2021 [Member]
Debt Instrument [Line Items]
Total principal	$ 873,609	873,609
Interest rate on debt instrument (as a percent)	5.75%
6.25% Senior Notes due 2023 [Member]
Debt Instrument [Line Items]
Total principal	$ 408,296	408,296
Interest rate on debt instrument (as a percent)	6.25%				6.25%
6.625% Senior Notes due 2026 [Member]
Debt Instrument [Line Items]
Total principal	$ 1,000,000	$ 1,000,000
Interest rate on debt instrument (as a percent)	6.625%			6.625%

LONG-TERM DEBT (Credit agreemen

LONG-TERM DEBT (Credit agreement) (Details) - Credit Agreement [Member] $ in Millions	6 Months Ended
	Jun. 30, 2019USD ($)
Debt Instrument [Line Items]
Maximum borrowing capacity of credit facility	$ 2,250
Maximum aggregate commitments	1,750
Borrowing capacity of credit facility, net of letter of credit	1,700
Outstanding borrowings under credit facility	40
Letters of credit borrowings outstanding	2
Portion of line of credit available for issuance of letters of credit	50
Amount of revolving credit agreement available for additional letters of credit under the agreement	$ 48
Weighted average interest rate	4.40%
Base Rate [Member]
Debt Instrument [Line Items]
Basis points added to reference rate (as a percent)	0.50%
LIBOR [Member]
Debt Instrument [Line Items]
Basis points added to reference rate (as a percent)	1.00%

LONG-TERM DEBT (Margin rates an

LONG-TERM DEBT (Margin rates and commitment fees) (Details) - Credit Agreement [Member]	6 Months Ended
	Jun. 30, 2019USD ($)
Debt Instrument [Line Items]
Retained earnings free from restrictions	$ 0
Minimum consolidated current assets to consolidated current liabilities ratio	1
Total debt to EBITDAX ratio	4
Base Rate [Member]
Debt Instrument [Line Items]
Applicable Margin for Loans (as percent)	0.50%
Less than 0.25 to 1.0 [Member]
Debt Instrument [Line Items]
Range, less than	0.25
Commitment Fee (as a percent)	0.375%
Less than 0.25 to 1.0 [Member] | Base Rate [Member]
Debt Instrument [Line Items]
Applicable Margin for Loans (as percent)	0.50%
Less than 0.25 to 1.0 [Member] | Eurodollar [Member]
Debt Instrument [Line Items]
Applicable Margin for Loans (as percent)	1.50%
Greater than or equal to 0.25 to 1.0 but less than 0.50 to 1.0 [Member]
Debt Instrument [Line Items]
Range, greater than or equal to	0.25
Range, less than	0.50
Commitment Fee (as a percent)	0.375%
Greater than or equal to 0.25 to 1.0 but less than 0.50 to 1.0 [Member] | Base Rate [Member]
Debt Instrument [Line Items]
Applicable Margin for Loans (as percent)	0.75%
Greater than or equal to 0.25 to 1.0 but less than 0.50 to 1.0 [Member] | Eurodollar [Member]
Debt Instrument [Line Items]
Applicable Margin for Loans (as percent)	1.75%
Greater than or equal to 0.50 to 1.0 but less than 0.75 to 1.0 [Member]
Debt Instrument [Line Items]
Range, greater than or equal to	0.50
Range, less than	0.75
Commitment Fee (as a percent)	0.50%
Greater than or equal to 0.50 to 1.0 but less than 0.75 to 1.0 [Member] | Base Rate [Member]
Debt Instrument [Line Items]
Applicable Margin for Loans (as percent)	1.00%
Greater than or equal to 0.50 to 1.0 but less than 0.75 to 1.0 [Member] | Eurodollar [Member]
Debt Instrument [Line Items]
Applicable Margin for Loans (as percent)	2.00%
Greater than or equal to 0.75 to 1.0 but less than 0.90 to 1.0 [Member]
Debt Instrument [Line Items]
Range, greater than or equal to	0.75
Range, less than	0.90
Commitment Fee (as a percent)	0.50%
Greater than or equal to 0.75 to 1.0 but less than 0.90 to 1.0 [Member] | Base Rate [Member]
Debt Instrument [Line Items]
Applicable Margin for Loans (as percent)	1.25%
Greater than or equal to 0.75 to 1.0 but less than 0.90 to 1.0 [Member] | Eurodollar [Member]
Debt Instrument [Line Items]
Applicable Margin for Loans (as percent)	2.25%
Greater than or equal to 0.90 to 1.0 [Member]
Debt Instrument [Line Items]
Range, greater than or equal to	0.90
Commitment Fee (as a percent)	0.50%
Greater than or equal to 0.90 to 1.0 [Member] | Base Rate [Member]
Debt Instrument [Line Items]
Applicable Margin for Loans (as percent)	1.50%
Greater than or equal to 0.90 to 1.0 [Member] | Eurodollar [Member]
Debt Instrument [Line Items]
Applicable Margin for Loans (as percent)	2.50%

LONG-TERM DEBT (Summary of seni

LONG-TERM DEBT (Summary of senior notes and convertible senior notes) (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018	Dec. 31, 2017	Mar. 31, 2015
Debt Instrument [Line Items]
Carrying value of debt instrument	$ 2,883,980	$ 2,843,980
1.25% Convertible Senior Notes due 2020 [Member]
Debt Instrument [Line Items]
Carrying value of debt instrument	$ 562,075	562,075
Interest rate on debt instrument (as a percent)	1.25%			1.25%
Debt maturity date	Apr. 1, 2020
5.75% Senior Notes due 2021 [Member]
Debt Instrument [Line Items]
Carrying value of debt instrument	$ 873,609	873,609
Interest rate on debt instrument (as a percent)	5.75%
Debt maturity date	Mar. 15, 2021
Make-whole redemption date	Dec. 15, 2020
6.25% Senior Notes due 2023 [Member]
Debt Instrument [Line Items]
Carrying value of debt instrument	$ 408,296	408,296
Interest rate on debt instrument (as a percent)	6.25%			6.25%
Debt maturity date	Apr. 1, 2023
Make-whole redemption date	Jan. 1, 2023
6.625% Senior Notes due 2026 [Member]
Debt Instrument [Line Items]
Carrying value of debt instrument	$ 1,000,000	$ 1,000,000
Interest rate on debt instrument (as a percent)	6.625%		6.625%
Debt maturity date	Jan. 15, 2026
Make-whole redemption date	Oct. 15, 2025

LONG-TERM DEBT (Senior notes) (

LONG-TERM DEBT (Senior notes) (Details) - USD ($) $ in Thousands, shares in Millions	1 Months Ended	3 Months Ended	6 Months Ended		12 Months Ended
	Jan. 31, 2018	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2016	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2015	Sep. 30, 2013
Debt Instrument [Line Items]
Gain (loss) on extinguishment of debt		$ (808)		$ (31,968)
Total principal			$ 2,883,980			$ 2,843,980
Repurchase of notes				$ 990,023
Senior Notes [Member]
Debt Instrument [Line Items]
Percentage of redemption price			100.00%
Aggregate principal amount converted into shares					$ 807,000
Number of shares upon settlement of conversion					19.8
5.0% Senior Notes due 2019 [Member]
Debt Instrument [Line Items]
Notes Issued										$ 1,100,000
Interest rate on debt instrument (as a percent)			5.00%							5.00%
Notes repurchased, principal amount	$ 961,000
Percentage of redemption price	102.976%
Gain (loss) on extinguishment of debt	$ (31,000)
Aggregate principal amount converted into shares					$ 139,000
Total principal							$ 0
Repurchase of notes	$ 1,000,000
5.75% Senior Notes due 2021 [Member]
Debt Instrument [Line Items]
Interest rate on debt instrument (as a percent)			5.75%
Debt, effective interest rate			5.50%
Aggregate principal amount converted into shares					326,000
Total principal			$ 873,609			873,609
5.75% Senior Notes due 2021, Par [Member]
Debt Instrument [Line Items]
Notes Issued										$ 800,000
Interest rate on debt instrument (as a percent)										5.75%
5.75% Senior Notes due 2021, Premium [Member]
Debt Instrument [Line Items]
Notes Issued										$ 400,000
Interest rate on debt instrument (as a percent)										5.75%
Premium as a percentage of par										101.00%
6.25% Senior Notes due 2023 [Member]
Debt Instrument [Line Items]
Notes Issued									$ 750,000
Interest rate on debt instrument (as a percent)			6.25%						6.25%
Aggregate principal amount converted into shares					342,000
Total principal			$ 408,296			408,296
6.625% Senior Notes due 2026 [Member]
Debt Instrument [Line Items]
Notes Issued								$ 1,000,000
Interest rate on debt instrument (as a percent)			6.625%					6.625%
Total principal			$ 1,000,000			1,000,000
1.25% Convertible Senior Notes due 2020 [Member]
Debt Instrument [Line Items]
Notes Issued			$ 562,075			562,075			$ 1,250,000
Interest rate on debt instrument (as a percent)			1.25%						1.25%
Debt, effective interest rate			5.60%
Unamortized debt discount			$ 17,950			29,504			$ 238,000
Aggregate principal amount converted into shares					$ 688,000
Number of shares upon settlement of conversion					17.8
Total principal			$ 562,075			$ 562,075

LONG-TERM DEBT (2020 Convertibl

LONG-TERM DEBT (2020 Convertible senior notes) (Details) $ / shares in Units, $ in Thousands	1 Months Ended	6 Months Ended
	Mar. 31, 2015USD ($)	Jun. 30, 2019USD ($)item$ / shares	Dec. 31, 2018USD ($)
Debt Instrument [Line Items]
Debt finance cost		$ 19,850	$ 22,665
Carrying value of debt instrument		2,883,980	2,843,980
1.25% Convertible Senior Notes due 2020 [Member]
Debt Instrument [Line Items]
Principal	$ 1,250,000	$ 562,075	562,075
Interest rate on debt instrument (as a percent)	1.25%	1.25%
Net proceeds	$ 1,200,000
Debt finance cost	25,000	$ 1,409	2,340
Carrying value of debt instrument		$ 562,075	562,075
Minimum days within 30 consecutive days of trading, where percent of conversion price exceed agreed upon percentage | item		20
Consecutive trading days | item		30
Conversion ratio		0.0064102
Conversion price per $1,000 principal amount of notes | $ / shares		$ 156
Debt, effective interest rate		5.60%
Estimated fair value of Notes	1,000,000
Debt discount	$ 238,000	$ 17,950	$ 29,504
1.25% Convertible Senior Notes due 2020 [Member] | Convertible Senior Notes Conversion Scenario1 [Member]
Debt Instrument [Line Items]
Minimum conversion price percentage used to determine settlement of conversion		130.00%
1.25% Convertible Senior Notes due 2020 [Member] | Convertible Senior Notes Conversion Scenario2 [Member]
Debt Instrument [Line Items]
Period after measurement period used for convertible senior notes		5 days
Debt Instruments Convertible Threshold Consecutive Trading Days		5 days
Threshold percentage of product of stock price and conversion rate		98.00%

LONG-TERM DEBT (Schedule of con

LONG-TERM DEBT (Schedule of convertible senior notes) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018	Mar. 31, 2015
Debt Instrument [Line Items]
Less: unamortized debt issuance costs	$ (19,850)		$ (19,850)		$ (22,665)
Interest expense	48,728	$ 48,331	96,827	$ 101,230
1.25% Convertible Senior Notes due 2020 [Member]
Debt Instrument [Line Items]
Principal	562,075		562,075		562,075	$ 1,250,000
Less: unamortized note discount	(17,950)		(17,950)		(29,504)	(238,000)
Less: unamortized debt issuance costs	(1,409)		(1,409)		(2,340)	$ (25,000)
Net carrying value	542,716		542,716		530,231
Interest expense	7,574	$ 7,258	15,068	$ 14,439
Equity Component Of Convertible Senior Note [Member]
Debt Instrument [Line Items]
Less: unamortized debt issuance costs	(5,000)		(5,000)		(5,000)
Equity component	$ 136,522		136,522		136,522
Equity component of convertible debt, deferred taxes			$ 50,000		$ 50,000

LONG-TERM DEBT (Security and gu

LONG-TERM DEBT (Security and guarantees (Details)	6 Months Ended
	Jun. 30, 2019
LONG-TERM DEBT [Abstract]
Percentage of owned subsidiaries	100.00%

ASSET RETIREMENT OBLIGATIONS (D

ASSET RETIREMENT OBLIGATIONS (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Asset Retirement Obligations
Asset retirement obligations, current portion	$ 3,000	$ 4,000
Reconciliation of the Company's asset retirement obligations
Balance at the beginning of the period	135,834
Additional liability incurred	1,982
Revisions to estimated cash flows	(7,511)
Accretion expense	5,819
Obligations on sold properties	(310)
Liabilities settled	167
Balance at the end of the period	$ 135,981

DERIVATIVE FINANCIAL INSTRUME_3

DERIVATIVE FINANCIAL INSTRUMENTS (Derivative instruments) (Details) - Crude Oil [Member]	Jul. 31, 2019bbl	Jun. 30, 2019bblUSD ($)$ / bbl
Derivative Financial Instruments [Line Items]
Aggregate notional amount of price risk derivatives (in Bbl) | $		11,612,000
Collars [Member] | Jul - Dec 2019 [Member]
Derivative Financial Instruments [Line Items]
Aggregate notional amount of price risk derivatives (in Bbl) | bbl		5,400,000
Derivative, Floor Price (in dollars per Bbl)		52.56
Derivative, Cap Price (in dollars per Bbl)		75.17
Collars [Member] | Jan - Jun 2020 [Member]
Derivative Financial Instruments [Line Items]
Aggregate notional amount of price risk derivatives (in Bbl) | bbl		728,000
Derivative, Floor Price (in dollars per Bbl)		55
Derivative, Cap Price (in dollars per Bbl)		67.33
Swap [Member] | Jul - Dec 2019 [Member]
Derivative Financial Instruments [Line Items]
Aggregate notional amount of price risk derivatives (in Bbl) | bbl	250,000	3,300,000
Derivative, Swap Type, Average Fixed Price (in dollars per Bbl)		61.43
Swap [Member] | Jan - Jun 2020 [Member]
Derivative Financial Instruments [Line Items]
Aggregate notional amount of price risk derivatives (in Bbl) | bbl		2,184,000
Derivative, Swap Type, Average Fixed Price (in dollars per Bbl)		58.88

DERIVATIVE FINANCIAL INSTRUME_4

DERIVATIVE FINANCIAL INSTRUMENTS (Narrative) (Details) - USD ($) $ in Thousands	Feb. 01, 2018	Jun. 30, 2018
Derivative Financial Instruments [Line Items]
Payment to settle future minimum volume commitments		$ 61,036
Crude Oil Sales And Delivery Contract [Member]
Derivative Financial Instruments [Line Items]
Derivative liability	$ 0
Payment to settle future minimum volume commitments	$ 61,000

DERIVATIVE FINANCIAL INSTRUME_5

DERIVATIVE FINANCIAL INSTRUMENTS (Effects of commodity derivative instruments) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Derivative Financial Instruments [Line Items]
(Gain) Loss Recognized in Income	$ (24,877)	$ 103,483	$ 38,028	$ 156,147
Not Designated as ASC 815 Hedges [Member]
Derivative Financial Instruments [Line Items]
(Gain) Loss Recognized in Income	(24,877)	103,483	38,028	156,147
Commodity contracts [Member] | Not Designated as ASC 815 Hedges [Member]
Derivative Financial Instruments [Line Items]
(Gain) Loss Recognized in Income	$ (24,877)	$ 103,483	$ 38,028	$ 156,147

DERIVATIVE FINANCIAL INSTRUME_6

DERIVATIVE FINANCIAL INSTRUMENTS (Location and fair value of asset derivatives) (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Gross amounts of derivative assets and gross amounts offset [Line Items]
Total financial assets	$ 25,971	$ 68,342
Commodity contracts [Member] | Not Designated as ASC 815 Hedges [Member]
Gross amounts of derivative assets and gross amounts offset [Line Items]
Gross Amounts of Recognized Assets	28,484	69,735
Gross Amounts Offset	(2,513)	(1,393)
Total financial assets	25,971	68,342
Commodity contracts [Member] | Not Designated as ASC 815 Hedges [Member] | Derivative Assets [Member]
Gross amounts of derivative assets and gross amounts offset [Line Items]
Gross Amounts of Recognized Assets	28,484	69,735
Gross Amounts Offset	(2,513)	(1,393)
Total financial assets	$ 25,971	$ 68,342

DERIVATIVE FINANCIAL INSTRUME_7

DERIVATIVE FINANCIAL INSTRUMENTS (Location and fair value of liability derivatives) (Details) - Commodity contracts [Member] - Not Designated as ASC 815 Hedges [Member] - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Gross amounts of derivative liabilities and gross amounts offset [Line Items]
Gross Amounts of Recognized Liabilities	$ 2,513	$ 1,393
Gross Amounts Offset	(2,513)	(1,393)
Other Current Liabilities [Member]
Gross amounts of derivative liabilities and gross amounts offset [Line Items]
Gross Amounts of Recognized Liabilities	2,513	1,393
Gross Amounts Offset	$ (2,513)	$ (1,393)

FAIR VALUE MEASUREMENTS (Summar

FAIR VALUE MEASUREMENTS (Summary of the Fair values and carrying value of debt instruments) (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Dec. 31, 2017	Mar. 31, 2015	Sep. 30, 2013
Fair Value [Member]
Debt Instrument [Line Items]
Debt Instrument, Fair Value Disclosure	$ 2,793,973	$ 2,601,722
Carrying Value [Member]
Debt Instrument [Line Items]
Debt Instrument, Fair Value Disclosure	$ 2,806,580	2,792,321
5.0% Senior Notes due 2019 [Member]
Debt Instrument [Line Items]
Interest Rate (as a percent)	5.00%				5.00%
1.25% Convertible Senior Notes due 2020 [Member]
Debt Instrument [Line Items]
Debt Instrument, Fair Value Disclosure				$ 1,000,000
Interest Rate (as a percent)	1.25%			1.25%
1.25% Convertible Senior Notes due 2020 [Member] | Fair Value [Member]
Debt Instrument [Line Items]
Debt Instrument, Fair Value Disclosure	$ 545,516	531,161
1.25% Convertible Senior Notes due 2020 [Member] | Carrying Value [Member]
Debt Instrument [Line Items]
Debt Instrument, Fair Value Disclosure	$ 542,716	530,231
5.75% Senior Notes due 2021 [Member]
Debt Instrument [Line Items]
Interest Rate (as a percent)	5.75%
5.75% Senior Notes due 2021 [Member] | Fair Value [Member]
Debt Instrument [Line Items]
Debt Instrument, Fair Value Disclosure	$ 880,161	829,929
5.75% Senior Notes due 2021 [Member] | Carrying Value [Member]
Debt Instrument [Line Items]
Debt Instrument, Fair Value Disclosure	$ 871,203	870,545
6.25% Senior Notes due 2023 [Member]
Debt Instrument [Line Items]
Interest Rate (as a percent)	6.25%			6.25%
6.25% Senior Notes due 2023 [Member] | Fair Value [Member]
Debt Instrument [Line Items]
Debt Instrument, Fair Value Disclosure	$ 408,296	375,632
6.25% Senior Notes due 2023 [Member] | Carrying Value [Member]
Debt Instrument [Line Items]
Debt Instrument, Fair Value Disclosure	$ 405,037	404,659
6.625% Senior Notes due 2026 [Member]
Debt Instrument [Line Items]
Interest Rate (as a percent)	6.625%		6.625%
6.625% Senior Notes due 2026 [Member] | Fair Value [Member]
Debt Instrument [Line Items]
Debt Instrument, Fair Value Disclosure	$ 960,000	865,000
6.625% Senior Notes due 2026 [Member] | Carrying Value [Member]
Debt Instrument [Line Items]
Debt Instrument, Fair Value Disclosure	$ 987,624	$ 986,886

FAIR VALUE MEASUREMENTS (Fair v

FAIR VALUE MEASUREMENTS (Fair value assets and liabilities measured on a recurring basis) (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Financial Assets
Total financial assets	$ 25,971	$ 68,342
Commodity contracts [Member]
Financial Assets
Financial assets - current	25,971	68,342
Level 2 [Member]
Financial Assets
Total financial assets	25,971	68,342
Level 2 [Member] | Commodity contracts [Member]
Financial Assets
Financial assets - current	$ 25,971	$ 68,342

FAIR VALUE MEASUREMENTS (Narrat

FAIR VALUE MEASUREMENTS (Narrative) (Details) - USD ($) $ in Thousands	Feb. 01, 2018	Jun. 30, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payment to settle future minimum volume commitments		$ 61,036
Crude Oil Sales And Delivery Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payment to settle future minimum volume commitments	$ 61,000

FAIR VALUE MEASUREMENTS (Reconc

FAIR VALUE MEASUREMENTS (Reconciliation-Level 3) (Details) - Level 3 [Member] $ in Thousands	6 Months Ended
	Jun. 30, 2018USD ($)
Reconciliation of changes in the fair value of financial assets (liabilities) designated as Level 3 in the valuation hierarchy
Fair value derivative, beginning of period	$ (63,278)
Unrealized gains (losses) on commodity derivative contracts included in earnings	2,242
Settlement of commodity derivative contracts	$ 61,036

FAIR VALUE MEASUREMENTS (Non-fi

FAIR VALUE MEASUREMENTS (Non-financial assets and liabilities measured at fair value on a nonrecurring basis) (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-recurring assets at fair value, impairment loss (before tax)	$ 0	$ 0

REVENUE RECOGNITION (Revenue Re

REVENUE RECOGNITION (Revenue Reclassification) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales	$ 426,264	$ 526,403	$ 815,753	$ 1,041,486
Oil sales [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales	403,870
NGL and natural gas sales [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales	$ 22,394

REVENUE RECOGNITION (Narrative)

REVENUE RECOGNITION (Narrative) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Revenue Recognition [Line Items]
Receivable balance	$ 157	$ 165
Revenue, Practical Expedient, Initial Application and Transition, Nondisclosure of Transaction Price Allocation to Remaining Performance Obligation [true false]	true
Minimum [Member]
Revenue Recognition [Line Items]
Payment received for product sales, period	1 month
Maximum [Member]
Revenue Recognition [Line Items]
Payment received for product sales, period	3 months

STOCK-BASED COMPENSATION (Narra

STOCK-BASED COMPENSATION (Narrative) (Details) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended
	May 31, 2019shares	Jun. 30, 2019USD ($)shares	Jun. 30, 2018USD ($)	Jun. 30, 2019USD ($)item$ / sharesshares	Jun. 30, 2018USD ($)$ / sharesshares	Dec. 31, 2016shares	Dec. 31, 2013shares
Share-based compensation disclosures [Line Items]
Number of shares authorized upon shareholder's approval							1,325,000
Number of additional shares authorized	3,000,000					1,375,000
Number of shares available for grant		3,449,427		3,449,427
Granted (in dollars per share) | $ / shares				$ 27.07
Stock compensation expense | $		$ 4	$ 5	$ 10	$ 12
Stock Option [Member]
Share-based compensation disclosures [Line Items]
Maximum number of Shares per employee				500,000
Maximum number of Shares per non-employee				25,000
Non Option award [Member]
Share-based compensation disclosures [Line Items]
Maximum number of Shares per employee				500,000
Service-based [Member]
Share-based compensation disclosures [Line Items]
Maximum number of Shares per non-employee				25,000
Granted (in shares)				389,303	234,949
Granted (in dollars per share) | $ / shares				$ 27.97	$ 31.92
Service-based [Member] | Share-based Payment Arrangement, Employee [Member]
Share-based compensation disclosures [Line Items]
Vesting (service) period				3 years
RSA [Member] | Share-based Payment Arrangement, Nonemployee [Member]
Share-based compensation disclosures [Line Items]
Vesting (service) period				1 year
RSU [Member]
Share-based compensation disclosures [Line Items]
Granted (in shares)				308,432
Market-based [Member]
Share-based compensation disclosures [Line Items]
Granted (in shares)				317,512	215,898
Granted (in dollars per share) | $ / shares				$ 25.97	$ 27.28
Target share granted percent, will be share-settled				100.00%
Market-based [Member] | Minimum [Member]
Share-based compensation disclosures [Line Items]
Possible multiplier of shares earned | item				0
Market-based [Member] | Maximum [Member]
Share-based compensation disclosures [Line Items]
Possible multiplier of shares earned | item				2
PSA [Member]
Share-based compensation disclosures [Line Items]
Vesting (service) period				3 years
PSU [Member]
Share-based compensation disclosures [Line Items]
Vesting (service) period				3 years

STOCK-BASED COMPENSATION (Assum

STOCK-BASED COMPENSATION (Assumptions) (Details) - Market-based [Member] - item	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of simulations	2,500,000	2,500,000
Expected volatility (as a percent)	72.95%	72.80%
Risk-free interest rate (as a percent)	2.60%	2.12%
Dividend yield (as a percent)	0.00%	0.00%

STOCK-BASED COMPENSATION (Summa

STOCK-BASED COMPENSATION (Summary of nonvested awards) (Details) - $ / shares	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Balance at the beginning of the period (in dollars per share)	$ 34.94
Granted (in dollars per share)	27.07
Vested (in dollars per share)	32.76
Forfeited (in dollars per share)	28.37
Balance at the end of the period (in dollars per share)	$ 31.77
Service-based [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Balance at the beginning of the period (in shares)	554,527
Granted (in shares)	389,303	234,949
Vested (in shares)	(335,911)
Forfeited (in shares)	(5,955)
Balance at the end of the period (in shares)	601,964
Granted (in dollars per share)	$ 27.97	$ 31.92
Market-based [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Balance at the beginning of the period (in shares)	503,696
Granted (in shares)	317,512	215,898
Vested (in shares)	(98,581)
Forfeited (in shares)	(111,199)
Balance at the end of the period (in shares)	611,428
Granted (in dollars per share)	$ 25.97	$ 27.28

INCOME TAXES (Narrative) (Detai

INCOME TAXES (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
INCOME TAXES [Abstract]
U.S. statutory income tax rate (as a percent)	21.00%	21.00%	21.00%	21.00%
Income tax expense		$ 0		$ 0
Valuation allowance					$ 152

EARNINGS PER SHARE (Reconciliat

EARNINGS PER SHARE (Reconciliation) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Basic Earnings (Loss) Per Share
Net income (loss) attributable to common shareholders, basic	$ (5,687)	$ 2,120	$ (74,612)	$ 17,132
Weighted average shares outstanding, basic	91,286	90,940	91,261	90,916
Earnings (loss) per common share, basic (in dollars per share)	$ (0.06)	$ 0.02	$ (0.82)	$ 0.19
Diluted Earnings (Loss) Per Share
Service-based awards, market-based awards and stock options		929		905
Weighted average shares outstanding, diluted	91,286	91,869	91,261	91,821
Earnings (loss) per common share, diluted (in dollars per share)	$ (0.06)	$ 0.02	$ (0.82)	$ 0.19

EARNINGS PER SHARE (Narrative)

EARNINGS PER SHARE (Narrative) (Details) security in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019shares	Jun. 30, 2018shares	Jun. 30, 2019securityshares	Jun. 30, 2018shares
Stock Option [Member]
Shares excluded from Earnings Per Share calculation [Line Items]
Stock options excluded from earnings per share calculation (in shares)	46,396	112,574	46,502	116,552
Service-based [Member]
Shares excluded from Earnings Per Share calculation [Line Items]
Antidilutive securities excluded from computation of earnings per share	182,583		293,505
Market-based [Member]
Shares excluded from Earnings Per Share calculation [Line Items]
Antidilutive securities excluded from computation of earnings per share	96,241		206,475
1.25% Convertible Senior Notes due 2020 [Member]
Shares excluded from Earnings Per Share calculation [Line Items]
Debt instrument, convertible, number of common stock | security			3.6

SUBSEQUENT EVENTS (Details)

SUBSEQUENT EVENTS (Details) - Subsequent Event [Member] - Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] - Oil and Gas Related Assets [Member] $ in Millions	Jul. 29, 2019USD ($)item	Jul. 02, 2019USD ($)item
Subsequent Event [Line Items]
Number of wells | item	137	58
Aggregate sale price		$ 26
Proceeds from sale of oil and gas properties	$ 27	$ 3